Like some people said, the attitude of people needs to change.
I just had a dungeon run with a fresh player, playing as a Black Mage. She was using Freeze like 80% of the time.
I explained her, that ice should only be used to refill MP and that she should use fire as much as possible.

Her answer: I like Ice, it's pretty, so I will use that. I play how I want.

I told her that she's holding us back, that she didn't input any damage.

Her second answer: Shut Up! Don't complain about my play style.


So it's really the attitude that needs to change, because then at-least they would be open to suggestions and criticism.