I want the core D&D books to be more explicitly designed to be tool box, with the base classes and lineages divorced as much as possible from setting-specific context. The risk would be that the flavor that sparks the imagination would be gone. I'd mitigate that by including three or more examples for each class, lineage, and even monster of how it might fit into various settings. Some guidance on what to include, exclude, and reskin to support various playstyles and fantasy genres. Building a campaign would involve making deliberate, thoughtful decisions about what to include.There seem to be a lot of foundational aspects of D&D as it was envisioned that, at least according to this and similar threads, a number of folks have a real problem with. I am forced to ask: what exactly do these folks want D&D to be? What's in the books? Specifically, because there's a lot of "I don't want/think this is boring/we could do without" this or that thing. I want to know what the actual game of D&D is supposed to be like, if all the people who have problems with this stuff get their way.
Serious question.
A benefit of that approach would be the opportunity to critically exam the old reflexive assumptions that D&D tends to import from previous incarnations and from popular culture as a whole.
That's what I want, but it wouldn't sell. As it stands, part of the popularity of D&D is that aspects of an unspecified default setting are baked into the core descriptors and makes it easier to start playing and easier for both players and DMs to have a fantasy world that they can sink their teeth into. I think that WotC could do a better job supporting the tool-box options without completely sacrificing the benefits of the implied, assumed default setting.
As for published settings, I want to see new and imaginative stuff, and,if old settings are updated to a new edition, I want interesting changes to those settings that make them worth revisiting. I have plenty of old settings that I can overlay new rules myself. I don't need them republished faithfully.