I found parry difficult to learn (but once it's down for an attack it's muscle memory) and I play fighting games where people count frames, where you have to make 300ms reactions out of multiple incoming prompts, and where you have 2 frames parry windows as opposed to E33's 16 frames (I believe).
The most frustrating thing is that the telegraphing is just not that clear. I actually wish they increased the FOV change so that it's more apparent when it's at its maximum.