No, the #SCOTUS didn't weaken EPA power to enforce the Clean Water Act. That gets backwards what the argument actually is.
The issue is that the CWA didn't authorize this power in the first place, so the EPA was acting outside of the Act.
If we want the EPA to have this much expanded authority, fine, that's what the democratic process is for. Let's have those discussions about how it would work, and the tradeoffs involved.
But that the EPA wasn't enforcing CWA in these cases is the entire core of the argument that the Agency lost.