You seem to be under the impression that straight couples in media are only ever married with 2.5 kids with a working father and stay at home mom but that really doesn't seem like it's been the case for a while.

While polyamory is probably still underrepresented, I'm not sure about your other examples. Also polyamory often includes at least one LGBTQ+ relationship so I'm not sure it makes your point. And a trans person in a heterosexual relationship falls at least half into LGBTQ+ by definition.

Most rom coms aren't about married couples with kids. Most sit coms show relationships where both partners work. The old trope of the dad who knows nothing about his kids is pretty dead at this point. Divorced and widowed couples show up a lot, too.

I don't think you're wrong that all kinds of relationships and gender expressions should be represented, but comparing it to the overall lack of LGBTQ+ rep out there... Well, one of these things is not like the other.

Also, my sister works and her husband is a stay at home dad. When people hear this they say "oh" and move on. When I mention my nephew is trans... Well the reaction is different. Very different. As stupid as it sounds, media representation plays a huge role in exposing people to things they don't get the chance to see often in their own lives (especially if you're from a small town). It's good for people to see trans characters they like and relate to before they find out about my nephew. I actually use it as a gauge to decide if I should tell people at all.

So long as straight is the assumption (or default), we are gonna need these kinds of spaces.