Of course the "art" art -- the part that is all about human creativity -- will always be there.
But lots of people in the art business aren't doing that. If you didn't have midjourney etc, what would you be doing for the throwaway work? Learn to design the stuff yourself, hire someone to do it on Upwork, or just not do it all? Some money likely will exchange hands there.
The throwaway work is worth pennies per piece to me at most. So I probably wouldn't do it at all if it wasn't for the generators.
And even when it comes to the generators, I typically just use the free options like open-source diffusion models, as opposed to something paid like Midjourney.
But lots of people in the art business aren't doing that. If you didn't have midjourney etc, what would you be doing for the throwaway work? Learn to design the stuff yourself, hire someone to do it on Upwork, or just not do it all? Some money likely will exchange hands there.