I can advocate for mcugen, and the non-gen stories I've loved I've also been reccing on my fic recs tag!

I've got a couple of absolute favorites, some of which are less soul-destroying than others:

Life of Crime is a long Avengers-as-supervillains AU with kinky poly stuff and the best ever Clint Barton narrative voice.

This, You Protect is a deeply hilarious Bucky post-WS "stalking Steve and making sure he's okay" WIP that is super, super worth following. He's so addicted to caffeine.

The Thrice-Tenth Kingdom is this heart-stopping Natasha grows up through the Red Room and the Winter Soldier glitches story.

Some of the Colors Have to Fade is, as I describe it, "murder buddies who bone and fall in love," Bucky and Natasha post-WS. Possibly my favorite thing in the fandom yet.