My gut is that's it's not "fatigue" as much as it just is getting too complex for casual fans. I think having to do "research" on backstory to just get what is going on might be a bridge to far for many people. Ahsoka is an odd case in that she is a very well known and liked character among even moderate fans (let alone die hards) but is virtually unknown among more casual SW watchers.
Then again some of the more stand alone Marvel shows - I'm thinking Ms. Marvel for example - haven't done as well as the connected ones so maybe I'm just wrong.
I do think Disney needs to have some non "part of a universe" stuff to put on D+ to counter balance, but they seem determined to strip away all that (e.g. recent announcements about Captain Nemo and Spiderwick Chronicles). They need to figure out their own Stranger Things, Ted Lasso, etc show.