Or to ensure players later in the expansion or alts even are able to get a group just as fast as you can. Separating the player pool like that wouldn't do any favors for anyone except the elitist jerks who CBA to help out a lowbie who's just trying to have fun. If this were a Mythic+ dungeon or a progression raid, I'd completely understand the mentality, but a Heroic dungeon that most groups can roflstomp their way through in their sleep....kicking people is pointless unless they're literally doing nothing (meaning they're AFK at the entrance the whole time.)
That said, if you're in gear appropriate to be doing 200k DPS, you should be doing 200k DPS....don't slack off. Just perform... all there is to it.