In a sane world, if Congress were okay delegating their responsibility, presumably they'd be okay rubber stamping whatever agencies sent their way (with the advantage that they could more thoroughly review something controversial). If they're not okay rubber stamping, then I suppose they weren't actually okay with delegating their responsibility.

Like surely the EPA could send them a 1 sentence bill saying "amend section H paragraph III to add chemical X at 30 ppb", and they could have it passed in a day if they have that trust.