Uhm... nnnnno, I actually feel like Endwalker was pretty well explained and paced. Could it be better, sure, and there were places I personally wish they'd have focused more (I literally just wanted a full-on Thavnair expansion), but I never felt like it was spending too much or too little time in an area that it ultimately needed. Again, I don't have enough of a feel for the OP's tastes to say they won't like Endwalker, because Endwalker does so much that it's hard to not like some of it.

Also, I am going to defend Necron, because while a fairly abrupt presence in the pure event-by-event story, he's a completely reasonable end state in terms of the themes and conceptual throughline of the game. FFIX is ultimately a game about how people deal with death; what better final boss than the embodiment of death itself? Admittedly, Necron was squaring a difficult circle in terms of embodying death itself without also embodying some other part of death; it makes a lot of sense to learn that the originally planned final boss was Hades, who would've very clearly represented death to everyone... but also would've given the wrong tonal implications, basically declaring the thematic enemy to be 'someday you will die and go to hell' rather than the more general 'someday you will die'.

Similar thing going with Endwalker's main enemy, actually. Speaking in terms of pure plot, sure, they're a relatively late arrival (although nowhere near as late as Necron was). But they're speaking to the closest thing FFXIV's got to an emotional throughline, so when you're thinking about it less as a pure 'events happen' story and more as a story that expresses emotions, ideals and concepts as well as events then they feel right at home, even if they turn up later.

...granted, I suppose from their largely detail-focused complaints I don't expect the OP to be someone with feelings that deep on Necron, so that character might be a miss for them, too. But again, a lot of stuff to like in Endwalker, I can't say they won't find something they'll enjoy. Maybe they were a big fan of the sort of stories that the Garlean Empire brought, which would naturally put them a bit off in Shadowbringers where they're practically the D-plot, but those guys come back in an interesting way in Endwalker.