People like that are generally the minority and the people that are like that will start complaint how there are no good players in the duty finder. There are things ya can do to off set not knowing an instance look up videos or starts for boss fights google is your friend. If a person is unwilling to do an instance with a new tank and would rather wait an hour que again it's their thing don't worry bout it

Ways to avoid being called a shitty tank
If you are a gld or a pld check out the guide for them found in this forum. Gives some pretty good insight how to do multi target pulls.

Mark your targets as you see fit if a dps pulls something that's not the number 1 target it's on them for not following numbers

Let your party know when it's cool for them to aoe

Click off regen when it's on you when pulling new groups of enemies

Keep you gear up to date

Remind your smn to turn off their pet stun abilities so you can interrupt without the mob being immune

My opinion