*edited
except this can still represent revenue for (some) artists...whilst being able to practice (to a degree) and being paid for it.
...which is just another way of saying that that work should be protected from automation. That's what arguing that tools that automate doing a thing will make people doing that thing less valuable as a paid labor is doing, it's arguing for protection from automation.
Also, do you have a source regarding that or is it from what you experience online?
Experience and a bit of hyperbole. Ask anyone who takes art commissions how often they get asked to do lewd to outright pornographic images though and you'll be surprised by the answer. But commissioned art/graphics for very specific carefully described things is all AI image generation is ever really going to replace, if only because that's the core of what it does - take a prompt and a big block of white noise and sort of digitally chisel away the bits that don't look like prompt until the result looks enough like prompt. The other obvious productive use case would be for rapid prototyping of visual design.
But then I'm old enough to remember people complaining that photoshop was destroying art. I'd be shocked if we couldn't find record of people back when it was new claiming photography was going to destroy art likewise.