When somebody brings up the invention of photoshop, they're not trying to disprove a point about paying salaries to the devs, and I am sure you knew that.
Rather, the problem is that these systems only exists today because of the involuntary contributions of the very same people who are likely to be put out of business.
It really is about the how the contributors to these systems are being treated. The coders that contributed to Photoshop are analogous to the artists whose work was used to train these models. The difference between them is that the former gave their consent to the contribution, and the latter did not.
That's it, that's the entire post. Never mind the "stolen artwork" argument, you still have people upset about "automating creativity".
So, like I said, it's one part of it.
When the artists whose work was stolen to train these models are compensated for that work then maybe its a "tiny part". Until then it is taking peoples work and using it to create an ultimate competitor in their own market that they cannot compete with. They now have to compete against themselves and they haven't even been paid for that "privilege".