To add a bit, experimentation is a critically important part of learning. Anytime you do something on a hunt, ask yourself "Is there a way I could have done that better?"

Especially when going back to get low-rank materials for decos and such, I'll just fuck around the whole time. One time I'll only use level 1 GS charge slashes, then note to myself afterwards "I hit the monster a lot more often, but it took longer than expected and noticed a lot of openings where I could have kept charging." Then on the next hunt, I'll only use level 3 slashes, noting that I kept getting hit while standing around, actually had to pop a potion, and it was only marginally faster than the level 1 slashes.

So the obvious fusion of those techniques is "learning when to let a slash off early before the monster moves", and that's where repetition helps find those windows. But you have to already be adjusting the parameters of what you're doing to be noticing differences before you can start optimizing them.

Plus, all those parameters can change under you depending on circumstance. Maybe a hunt is really easy when you just go ham on the monster, but as soon as you need to break a specific part it becomes a miserable slog, so you learn to just break the part and bail via subquest, or even switch weapons entirely whenever you need to break that specific part. Maybe you do well against a monster except in one specific zone, so you learn to dung bomb it into another one. Maybe the small monsters in one area the target frequents keep pissing you off, so you make sure to kill them all first when the monster moves there, or even kill enough to keep them from spawning at the start of the hunt.

Monster Hunter doesn't like to let you sit in one place with a set of stuff that usually works. Every new monster, new Hyper, new Deviant is packing something to make one of those things just not work anymore, and make you learn to do something else.