Actually hard DPS checks disagree with you on this, it's much less apparent now with echo but most raids (See: Coil) have some sort of DPS performance check.

Sure if you clear without issues you may have no way of knowing if they were doing their job adequately or not, but it becomes very apparent when you don't clear if certain DPS aren't pulling their weight, for example is the BLM using AoE to kill the Blackfires in T12 or are they spamming single target on the boss and now we're wiping the run?

The expectations of the party are usually stated in the PF before you join and the screening process is the ability to remove players from the group that aren't able to meet the requirements set in the PF, And actually for DF ilvl is the same thing really, it's a value that determines the minimum performance level (based on gear stats) capable of completing the content you queue for.

Item level is a hard check in the game preventing people from under-gearing or entering content they aren't ready for but only from a numbers side, as someone can still go in and face-roll their keyboard and wipe the party, So yes even the DF has some level of expectations you are required to meet.