There are ways to enforce it. Yeah, you won't be able to make everyone follow the rule, but it's the same with any law and any public policy and they're still valuable. You don't make campaigns against DUI because you expect everyone to stop doing it, as that's a nirvana fallacy, you make them because you expect them to reduce DUI.

Which tells a lot about how good they are. Slop is slop because it's bad, but a high quality PR isn't

With systems starting to move to watermarking tech a lot of them will actually be detectable.

Either way that doesn't make it a bad idea or less useful.

so the solution then is to just give up??

sorry but that's obviously nonsense, you can have unenforceable rules, god isn't going to smite you for doing so.