Damage / Buff calculations based on animation is problematic.

[Gilthas]

Asking players to accept it, is asking us to accept poor design and response time..

There are 2 potential cases..
1. SE don't know how to fix it.
2. It's a design choice.

Both are terrible.

Sorry but "you not liking something" isn't the same thing as "poor design".

People need to adapt to the game system instead of demanding that the game system be changed to suit their personal tastes.

Well this can also happen.
Along with complete animation cancelations.
Use a skill, half the animation is displayed, half of the GCD completes, then you find out that the skill didn't actually go off. This happens quite frequently with Shield Lob.
So yes, often skills are also unresponsive, which is another glaring issue entirely.

If this is happening frequently to you I suggest you check your internet connection. I only get this when I'm lagging. And no, not all lag is due to SE's servers.

Regardless, this has nothing to do with your original complaint, you're just going off on a tangent to support your "unresponsive" claim.