People are really missing the point here.
It's not about OP being bad at the fight, the game or whatever.

It's about the fact that, as someone else already said, FFXIVs communication between server and client is just plain awful and makes the game feel clunkier and slower than it is. I often see players, not bots no, lagging through the world and in most cases, where you, for example, kill a questmob it takes like 0.5 seconds for it to register.
In WoW, for example, I almost never had this problem. Except for BfA-regions, where everyone agreed the servers just couldn't handle this many players on the shard.
Been like this since I started playing in the ARR beta. There's no denying it.
Maybe you don't even notice it, if you don't play other MMOs. But it's there.

Now, you adjust to this little nuisance and enjoy and love the game anyway.
But sometimes stuff like this happens, where this little nuisance leads to someone failing something because it was kinda close, and then they are upset. Rightfully so.