But, how do I see things to you then? You want settings as reading material, which means the mechanics don't really matter, that's not why you're buying the books, but, you also want the mechanics updated, without changing the setting despite the fact that the original setting material was based on very different mechanics that don't really work in 5e.
That's a pretty difficult thing to satisfy. I mean, if that's true, then I cannot have a lot of stuff in the earlier settings since it didn't exist in the game at the time - no dwarven magic-users, heck, most races can't be most classes - for example. If we're going by that metric, what's the cutoff? Should Greyhawk only draw on material published before the boxed set? So, no PC drow allowed - since PC drow didn't appear until the Unearthed Arcana 1e? What should Vecna be? A lich? A demi-god? A major deity? Never minding the rather large number of deities that have been added to the setting since the boxed set was released. Should they be excised as well?
Any update to a setting is going to have to make any number of decisions. Where you draw that cut off line is never going to make everyone happy. It's impossible to update a setting to new mechanics without changing the sensibilities of the setting.