Don’t feel bad.
It doesn’t affect people in the dungeons you join.
It affects only people who are partied with you at the time you queue.
If you just join a dungeon queue normally, nobody gets any debuffs. It’s all normal.
But if you make a party with some friends and then queue as a party, and you are all twinked out so you blow the whole place up in 2 minutes, those friends don’t get much XP.
So don’t feel bad about queueing while XP-locked - you’re not affecting anyone else.