The difficulty hasn't necessarily even increased that much, they are just using more varied tells for mechanics. There is nothing in the msq dungeons that require fast reaction time, just about everything gives you at least 5 seconds to get into position, often even longer. The main difference is that there is less reliance on showing a big glowing orange danger area for every mechanic, which is a good thing. That's how the game gets stale, and Endwalker dungeons really suffered from it, even in instances where the tell was environmental, they'd still give an extra several seconds of orange ground so you never even had to learn it