I feel your pain. In the past I've had a hard time finding het romance, and questioned about it like it was rude for me to have a different/exclusive orientation for my character. With that said, I have rped girl/girl, male/male, poly, asexual, het love..I mean I'm very fluid and I love each one. But I do agree it's harder to find het but like previously stated above, I don't think it's advertised as much as lgbt+. Personally, I put it in my profile but I like action/adventure/open world RP way more and my romances have to make sense and with meaning, not flings.
But yeah, reach out to other people, they could be feeling the same way as you.