>But sometimes your work is put on Instagram without your knowledge or consent (eg by an Instagram aggregator account)

That's copyright infringement. You can't claim to own other people's work and then give license to others to use when you don't own the work.

Of course it is! It being illegal doesn't mean Instagram is incentivized to crack down on it

And if you're a tiny independent artist you also aren't well-resourced to do anything about it.

(Afaict the best thing we can do is maintain a culture that demands attribution)

I represent tiny independent artists and the best thing you can do is hope that some moneyed media company infringes your work. They never have an excuse and they always pay up.

But that's not what happens on Instagram

This isn't like some TV ad using a song they forgot to license

I've recovered for uses on Instagram

Sure, but it is quite difficult to prove your work was used in the models and it is also quite expensive legally while being very time consuming. So in practice does it matter? I still believe in presumption of innocence, but that isn't to say that it can't be exploited and that the system itself is expensive (monetarily and temporally). I think you're just oversimplifying the issue and dismissing before considering any nuance.

what am I dismissing? I think these AI companies are stealing these works. Nerds here are equivocating the creation of art with what LLM output, simply out of their own inexperience making art. It's terrible and I hate it.

I believe I misinterpreted, it sounded like you were just suggesting it was copyright and thus could empower the artist to sue the companies. As if the process was rather straightforward and thus the fault on the artist for not pursuing. I'll admit that I'm primed by other comments which do express this sentiment explicitly. Sorry if I misunderstood.