I'm not sure this is something that you can ever really fix because the cause isn't simple and so a solution would have to be just as complicated and multifaceted. LS die because they can't really enforce participation, and dedicated mentoring would end up becoming a job where you are essentially forcing RP connections (which will make one of the points I'm about to make that much harder to deal with).
If you're a not-so-well-known RPer here like myself want to become more popular within the community, it's one of those "be patient, it WILL take lots of time" situations, and the amount of time required grows the older that community is. Let me explain and talk as one of those people on the outside looking in:
Cliques happen and often times they are unintentional. Sure, some people are snobs, but for the most part - as it has been pointed out - some people simply don't have enough free time left over from real life and RP and so they can't commit to learning to RP with another character all over again (and each RP connection is, in fact, a learning experience). Plus RPing in an MMO is fully-engaging: it's not like forum or post RP where you can respond at your leisure and write as long as you have the right tool to do so. In an MMO you have to glue yourself to your computer. This limits free time even more.
Then consider what RP is like on an MMO. No game is EVER made for RPers or with RP at the forefront of its design goals, which means each one ends up turning into a conflicting, messy play pen with pot-holes in the lore, conflicts between game mechanics and immersion-breaking explanations for those mechanics, etc (there is no greater proof than all the lore discussions and arguments that happen here on RPC lol). Finding good RP, as a result, is simply hard. Also maintaining good RP is equally difficult if not more so because people will sometimes poof from the game (and many never return).
That last point I want to highlight further because FF14 has such a long and hard past, and as a result, so too will its RPers. Some of us started at 2.0 but there are others who have been around and RPing since 1.0; that's a lot to compete with. Think about all the connections and plots that people have worked on only to have them abandoned by the other people involved (either mid-plot, or afterwards). Heck I can go through the wiki and pick one  ACTIVE bio at random and see a list of connections and relationships which is likely over half full of characters who aren't even around anymore or are barely active, but based on the descriptions these were clearly involved relationships with stories behind each one. Also, think about all the plots that have going on for SO LONG and are simply too involved to bring in some random new face out of the blue. As a result, it's not hard to believe that good RPers tend to cling to those other good RPers who stick around for the long haul - they're like freakin' unicorns lol. And that, I've always felt, has the been the obstacle for the rest of us. VeteranA doesn't know Newbie, so Newbie could very well end up leaving FF14 after only a few months, so does veteranA really want to really dive into some serious RP with them especially when they have SuperPlot#1 with veterans B and C going on?
Frankly, I can't imagine trying to fit my character in with someone who has 4842735049 IC RP buddies, and have people here on the RPC hanging off their jock in every thread lol I mean, look at the fun games that we play here like "Characters mine have a crush on" or "Characters I want to RP with more" or "Let's draw pictures of each other" - it's the same popular characters featured over and over again. Who wants to be another face that someone else has to struggle to remember along with all of their FC buddies, RP linkshells, buddy lists, and the people here on RPC? The relationship, in the beginning, would likely become an obligation, and being a chore is not something any of us enjoy which is where the newbies contribute to the failing inclusivity of the community. In the dynamic of established-RP and unknown-RPer, it will likely be the "new guy" who is going to feel that way because he or she is pretty much a side project for the person who already has a bunch of storylines going on and is just. flatout. EXHAUSTED lol A person can sense when they are being a chore to RP with, and it robs of them of the inspiration to continue. So they leave, and they take personal offense and say that the veteran wasn't trying.
And that's what I mean by multifaceted cause: it's not just the popular kids' fault and it's not just the newbies' fault. It's just unfair circumstances because that's life sometimes. I know we live in an age now where every kid gets a trophy just for showing up, but the universe does not exist to please us. Remembering and being rationale about that is what helps keep me from being frustrated in my attempts to branch out more here on the RPC and in-game and it's something I encourage others to do as well: when you remind yourself that people aren't trying to form cliques, you don't get mad when you see it happen.
That's the only advice I can offer to my fellow "unknowns:" stiffen your upper lip, be level-headed, and be patient. Alternatively - and this isn't a jab at those of you who do have popular characters because obviously you've put the time and energy into your RP and should be proud of being in demand - don't try to get in with the veteran characters or RPers in the first place; don't make that a goal. Try to RP with other people who aren't so well-established in the community instead.
And always try to match up your time-zones.
If you're a not-so-well-known RPer here like myself want to become more popular within the community, it's one of those "be patient, it WILL take lots of time" situations, and the amount of time required grows the older that community is. Let me explain and talk as one of those people on the outside looking in:
Cliques happen and often times they are unintentional. Sure, some people are snobs, but for the most part - as it has been pointed out - some people simply don't have enough free time left over from real life and RP and so they can't commit to learning to RP with another character all over again (and each RP connection is, in fact, a learning experience). Plus RPing in an MMO is fully-engaging: it's not like forum or post RP where you can respond at your leisure and write as long as you have the right tool to do so. In an MMO you have to glue yourself to your computer. This limits free time even more.
Then consider what RP is like on an MMO. No game is EVER made for RPers or with RP at the forefront of its design goals, which means each one ends up turning into a conflicting, messy play pen with pot-holes in the lore, conflicts between game mechanics and immersion-breaking explanations for those mechanics, etc (there is no greater proof than all the lore discussions and arguments that happen here on RPC lol). Finding good RP, as a result, is simply hard. Also maintaining good RP is equally difficult if not more so because people will sometimes poof from the game (and many never return).
That last point I want to highlight further because FF14 has such a long and hard past, and as a result, so too will its RPers. Some of us started at 2.0 but there are others who have been around and RPing since 1.0; that's a lot to compete with. Think about all the connections and plots that people have worked on only to have them abandoned by the other people involved (either mid-plot, or afterwards). Heck I can go through the wiki and pick one  ACTIVE bio at random and see a list of connections and relationships which is likely over half full of characters who aren't even around anymore or are barely active, but based on the descriptions these were clearly involved relationships with stories behind each one. Also, think about all the plots that have going on for SO LONG and are simply too involved to bring in some random new face out of the blue. As a result, it's not hard to believe that good RPers tend to cling to those other good RPers who stick around for the long haul - they're like freakin' unicorns lol. And that, I've always felt, has the been the obstacle for the rest of us. VeteranA doesn't know Newbie, so Newbie could very well end up leaving FF14 after only a few months, so does veteranA really want to really dive into some serious RP with them especially when they have SuperPlot#1 with veterans B and C going on?
Frankly, I can't imagine trying to fit my character in with someone who has 4842735049 IC RP buddies, and have people here on the RPC hanging off their jock in every thread lol I mean, look at the fun games that we play here like "Characters mine have a crush on" or "Characters I want to RP with more" or "Let's draw pictures of each other" - it's the same popular characters featured over and over again. Who wants to be another face that someone else has to struggle to remember along with all of their FC buddies, RP linkshells, buddy lists, and the people here on RPC? The relationship, in the beginning, would likely become an obligation, and being a chore is not something any of us enjoy which is where the newbies contribute to the failing inclusivity of the community. In the dynamic of established-RP and unknown-RPer, it will likely be the "new guy" who is going to feel that way because he or she is pretty much a side project for the person who already has a bunch of storylines going on and is just. flatout. EXHAUSTED lol A person can sense when they are being a chore to RP with, and it robs of them of the inspiration to continue. So they leave, and they take personal offense and say that the veteran wasn't trying.
And that's what I mean by multifaceted cause: it's not just the popular kids' fault and it's not just the newbies' fault. It's just unfair circumstances because that's life sometimes. I know we live in an age now where every kid gets a trophy just for showing up, but the universe does not exist to please us. Remembering and being rationale about that is what helps keep me from being frustrated in my attempts to branch out more here on the RPC and in-game and it's something I encourage others to do as well: when you remind yourself that people aren't trying to form cliques, you don't get mad when you see it happen.
That's the only advice I can offer to my fellow "unknowns:" stiffen your upper lip, be level-headed, and be patient. Alternatively - and this isn't a jab at those of you who do have popular characters because obviously you've put the time and energy into your RP and should be proud of being in demand - don't try to get in with the veteran characters or RPers in the first place; don't make that a goal. Try to RP with other people who aren't so well-established in the community instead.
And always try to match up your time-zones.