This is coming from someone who considers themselves to be a 'casual'
I mean this in the nicest way possible but if you have been playing this game long enough to be at level 100 you should know your basics in this game, including the fact that you are going to die while learning and that normal raids were made more difficult than the normal trials because they are optional content that you don't even ever have to touch.
The only way you will not learn is if you aren't paying attention or are actively trying your hardest to not absorb the clear information the fights are giving you, it's as simple as that.