I basically really enjoyed the MSQ dungeons personally but I can see why they're a problem.

In my experience it boils down to three of the bosses; Maulskull, Vasoconstrictor (they're not actually called that but that's their one big move so that's their name now), and Alexandria Boss 1. They're all very punishing and I've been in tons of parties that wipe repeatedly on it. Personally, I am okay with wiping repeatedly to a boss to learn it and eventually beat it, but not while I'm following a story. In a way, this was all mitigated, ironically, by the fact Dawntrail's MSQ is kind of divisive to begin with and I didn't care so much but I was one of the people who hated the initial version of Out in the Cold because it was thoroughly frustrating and took me out of a really important part of the story. When the story is good, I actually do not want to do anything hard.

Wiping is great when I want to do hard things, but not when I'm following an FF story. I think people are forgetting that this is technically a main line Final Fantasy game. Even as a small child, I don't recall ever having difficulty while following the main story of a Final Fantasy game. Simply put, if the proximate plot point is "We must rescue my girlfriend from the edgy tower of darkness to stop her destroying the world", wiping 15 times to Sephiroth while learning his attack patterns is frustrating, even if it makes sense because Sephiroth is very cool and, in a vacuum, would be a very fun boss to fight. Contrast this to something like Elden Ring; the story exists and is there for you to piece together but it's never building so much momentum or magnetism up for itself that it gets in the way of you side tracking to spend five hours dying to some random guy in a cave.

So obviously, Alexandria Boss 1 is the standout among these. Great boss. Tons of fun. Way too hard for MSQ. You need to make five precise movements which need to secondarily respect an AoE that will go off sometimes before and sometimes after the tic-tac-toe telegraph depending on when the inhaling sequence starts, in close proximity to the boss and all the effects going on around it. It's then immediately followed up with a tank buster for the tank and a stack for everyone else. This is straight up harder to execute than most of the stuff the first Extreme throws at you. The tank's probably fine because the tank's always fine. If one person died and another got hit, the person who got hit is likely to die without intervention of some kind. I know how to throw a thing onto someone else as a tank but I struggle to execute that and hell if I've seen a tank do that for anybody during that sequence. If two people died and you're the healer, have your cooldowns up and know exactly what to do, you can survive the stack solo by topping off, throwing on a shield and mitigating, but that's also asking a lot. Someone is at minimum healing an extreme before that's being asked of them.