Agreed, 5.5 ultimately failed both groups. Folks who wanted substantive changes improving quality of life rightly shake their heads at all the obvious failures at doing so. Folks who were sold a marketer's wet dream version of backwards "comparability"that was more like an overinflated hyped up binary compatibility were never going to get what they were told to expect.I'm not sure what "a lot of people" means, or if those are the same "lot of people" who demanded backwards compatibility (allegedly.) I don't think the surveys gaslit WotC about backwards compatibility, I think WotC gaslit the players about backwards compatibility, which was clearly a strong desire and which wasn't really delivered, even though it was promised. I don't think the backwards compatibility is any more real than it was between 3e and 3.5, or between 3.5 and Pathfinder. Sure, the systems are quite similar, but the details are all different. Which is probably why when talking freely, the WotC call it 5.5. They know it's not really backwards compatible.
Maybe the setting books can address some of that maybe not. Although the lack of any indication that those are a planned way of doing so in any particular way doesn't give me high expectations of seeing them trying to do som