We have become D&D (-ish) SE
Right now, of the 50 latest questions, only two are not about D&D or D&D clones (D&D 5e and 3.5e, PF 1e & 2e). That is 96% D&Dish.
It's been that way in the past but I think we all hoped it would bybe a hype phase after launch. But it's way past launch now.
For me that's sad because there are so many other systems out there and reading questions about them is sometimes the way that I get interested.
It seems the effect is maybe self-reinforcing. Good answers attract more questions of that kind. A Catch-22.
I don't know how to solve it, but I see this kind of one-sided eco-system as a problem.