I wouldn't read too much into xi's server merges and population decline. After all, the games been around for a very long time, had a very good run, and it's fairly reasonable to think it has come close to running its course at this point with or without those changes. Although I agree with you inasmuch as if I were still around, I would be unable to deal with them making everything I'd done over so many years irrelevant and I would leave. As is, I left just a bit before the "new" content. The game already felt like it was closer to over than not with 14 on the way, along with a whole bunch of next gen games from other companies, and I didn't want to keep working for things that would vanish with an old game. To be fair, there's plenty of other reasons I left as well, but no need to get into that here.
To the people acting like raids are bad because they make items exclusive to endgame players... I don't get that at all. It's a /much/ more lenient system than xi had. Anyone with an LS has a good shot at getting the raid items because no one can block them. If you don't have the time for that... sure... you won't get it. But the game can't cater to everyone (and that cuts both ways. 14 has/will get more concessions for casual solo players as well, which hardcore endgame people don't need and might even dislike).
Open world NM's are great. And I think we should have them too/keep them. But XI really dropped the ball on that by having it's system reward people who broke the Terms of Service. I don't want to do that again, even though I came out "on top" of it in xi. A design that rewards players who break the ToS is poor. I honestly think the new one with almost constant repops on Uraeous/etc isn't that bad. It's another system that lets everyone have access to the gear - provided they're competent enough to handle the challenge.
What I'd /REALLY/ like to see is to have the difficulty of those constant NMs ramped up greatly in the future though, to compensate for their constant presence. That way /anyone/ can get the gear without cheating or breaking the ToS, but only if they're part of a set of 8 decent players (or perhaps 16 if/when alliances are allowed). Harder fights requiring perfect timing etc. But not fights that are impossible to get to/initiate. You can say sitting in the Aery every day of the week for 2 or 3 hours was good social time... and to some extent that was true. But to a much larger extent it was a very poor use of real life time on my part that I chose to partake in nonetheless. I don't want to do that again if I don't have to. (And don't think I /would/ do it again, period).
So would I quit if they add more instanced things? Not really. I don't want to see the game become an instance fest like WoW or anything, but I think having a few around is quite healthy for variety, and adds an enjoyable way to xp/get gear/do stuff on /YOUR/ schedule, and not an arbitrary pop timer. These games can be very time consuming if you take them "seriously". But if you're able to manage that time somewhat with your ls and do Raid X on Y day of the week, while going after NM A (who's always up) on B day of the week, you can handle that time commitment pretty easily, without letting it get to your more serious real life affairs.