There are enough DPS players. The question is whether the group finder feels like adding those players to an ongoing run. Anyone who has played dungeons for a while know the group finder works in mysterious ways. You may be missing a DPS, you may tell your friend to queue, yet even when your friend queues, the capricious group finder may decide to have your friend wait for a fresh full group instead of yours. While you just wait or continue with 4 people because the group finder blacklisted you? Nobody knows.
There’s a difference between the group not clearing the dungeon and one person not pulling their own weight. It also doesn’t have to be the end of the world for anyone to give feedback about the dungeon gating system being worthless in its current state. It’s not constructive to shoot down the feedback of others through irrelevant comparisons and logical extremes.
You also have a problem. You’re treating the IP thresholds as gospel. It’s just another gating method like the Gatekeeper and it’s just as flawed, if not more. Item Power is a rubbish gating mechanic. Even when we disregard player skill, it doesn’t account for passives, capstones, extraordinary effects, gear pips, agent bonuses, etc. IP doesn’t care for anything other than how much time and/or money you wasted on the IP grind. It’s just arbitrary numbers set by Funcom and they are open to all manner of feedback and adjustment.
Most of the time, inexperienced players queue for the highest tier they can. Not because they had to. Not because they enjoy it the most. Not because they want to push themselves to the limit. Not because they calculated the XP/time and thought it would be the best for progression. Simply because the finder allowed them.
So it really irks me when you refer to this situation as “somebody must be penalized”. The only reason that somebody can run E10 is because the finder told them they could. It’s not “penalizing” if the finder instead told them they can’t. It’s just a change in the gating ruleset.