Hmm...I think you are missing the point.
We all know that those things happen, but mostly I personally advocate that people shouldn't be able to queue with gear that isn't strong enough for the content they queued for because in the end no matter how much skill they have or don't have they still can't ever do their role properly.
Like that one poster from another thread where the healer was too under geared in The Vault:
According to Rita it took 3 wipes until the group got lucky that RNG didn't target the healer so they could finally beat the boss. That bosses LB move is unavoidable damage so I highly doubt the development team intended you to get one shot by it and for it to end up one shotting the healer and wiping the entire group.
Obviously you need a certain amount of gear to do the content properly (and I'm not talking about the best gear; just somewhere near minimum to be able to safely survive mechanics and do enough DPS which SE's dev team should know what the limits should be for each duty) so not having an item level requirements seems silly tbh.
Adding it would be simple since many other DF duties have item level requirements already on them and it would protect against this type of time wasting that people run into.
No one is claiming that wasted time will never happen with PUGS in DF still...it just eliminates a few more circumstances which causes waste of time. No one claimed DF will be perfect if they change it, but it would still be a bit better off than it is now.
Simplest terms:
Not clearing because of player skill = Can't be fixed. Some players will be bad because they don't care to be good. Or if someone is new then we try to help them/teach them and keep trying.
Not clearing because the gear a player is wearing is not "strong" enough for the content = Easily fixed by adding more DF requirements. No logical reason to not fix this and avoid wasting time.