1. Yes, Exandria is the Starbucks of D&D in that it's way more available and heavily advertised. That doesn't make it the better product.
Nobody is saying Exandria is the be-all-end-all of settings. Within "standard D&D high fantasy published by WOTC" it's pretty decent, has some specific stuff going for it enumerated herein, and Wildemount in particular is a much better then average setting handbook for a DM to actually use. Expanding beyond that categorical division turns into kind of a lost cause, there's just so many possible settings (inclusive primarily of most DMs who want to step outside of primary published lines into creating their own).
Exandria is great for younger players, those who don't want to deal with certain subjects,
Ah yes, younger players who are notoriously into grand political fights; wars; complex grey areas around how societies deal with expansion and the disposed (sometimes bleeding into metaphysical questions); just like George Lucas determined when he made a prequel series about the fascinating topic of pan-galactic trade.
(what certain subjects are you alluding to? Exandria tends to have plenty of classic D&D stuff, it just does a better job of presenting many sides to an idea or conflict then stuff like FR)