>>149924325
It's the same issue there's always been. Animation is fucking expensive, and past a certain age kids don't want merch anymore (or, more pointedly, parents don't want to - or cant' - buy it for them), so only shows that can push merch for kids survive. Remember, even shit like Transformers and GI Joe and Ninja Turtles was only really ever aimed at the 12-and-below set, because that's where the toys went. 15-year-olds aren't buying toys. Normal ones, anyway.
There were exceptions in the late 90s, TV in general was taking a lot of new risks, so you had a lot of animation aimed at broader audiences, some even aimed at adults like the stuff MTV put out for a while. But then the mid-2000s economy tanked and everything started contracting so only sure bets got a chance to go forward more often than not. There were still a few bursts of life here and there but when Cartoon Network started broadcasting live action shows and Sci Fi Channel became a husk that produced shitty CGI monster-of-the-week movies with ads every 5 minutes, the writing was on the wall.
So at this point the current generation just hasn't had anything worth getting into, so the market's practically dead, at least among major producers. Your best hope is indie producers on youtube.