Huh.

Dungeons, trials and normal raids have not increased in difficulty. In fact, they are now easier to read, and we even got a red shiny text bar that tells people "Heyo hello there's a mech coming up". You're either out of touch, or out of the game loop.
Even with the "hurdur live service game" excuse, it is still an mmo game, where dungeons on the higher level are supposed to get broader and introduce more mechanics. Dawntrail, with many flaws on the main story, did it splendidly.
You do not need to know fight. You come to understand it, by seeing mechs resolve and thinking about where to stand on next time. It is not in fact a problem of the game, if you expect to queue up to level 100 content and get the same treatment as the Main Scenario roulette.
If you want casual content, consider Island Sanctuary. If you want to play casually at dungeons - learn.
Otherwise,