I just found this thread, so forgive me if I don't wade through 51(!) pages of comments before weighing in.
I was pretty close to done with WotC in November before any of the OGL stuff started circulating. I've found their design to be boring for a while now, and I find a lot of the lore, cosmology, and other thinking that comes with the D&D brand to be tedious. I do like d20-based, class-and-level adventure fantasy RPGs, however.
Hot take time: I don't like gith. I hate the blood war. I'm not a huge fan of beholders. I have no particular fondness any of the official D&D settings that aren't Eberron or a repurposed Magic: the Gathering setting, and even in that case, they've left all the best ones like Eldraine, Tarkir, Dominaria, and Alara on the table. I also haven't used a WotC monster book in years.
More mainstream takes: I really like a lot of the innovations that appear in Level Up. I like having a maneuver system, rare spells, "race" split into heritage and culture, exploration knacks, and so on. I like these as a player, GM, and designer, it bears mentioning.
And I have been a firm believer that all of the best design for supplements, settings, and the like has been coming from the 3PP community for over twenty years.
Why would I go back to D&D? WotC offers nothing I want.