I believe I understand what your position is regarding the concept of art vs non-art.
However, I think the main argument is less about the artistic merit of AI generated art and more about the impact on the ability for artists to be artists when one of the means of generating a means for a living is removed from them. The elevator music and office artwork pieces were the means for income for many that allowed for the pursuit of more complex and long term projects. It was art insomuch as it was a creative endeavor, but I'm not sure how many artists believed that such pieces were their true expression.
A lot of that is now quite easily replaceable by anyone with a bit of time, a few source sample images, some keyword manipulation, and a computer as "simple" as a MacBook. Music generation likely isn't far off, and I think Meta even demo'd some AI-Video generator.
Automation should serve the people, and I have no doubt that at some point in a nicer future it will be a boon where we can have "nice things" and a lot of expression that wasn't previously possible. In the interim, there is a slew of people whose living means are heavily at risk. Patreon, et. al., aren't going to be enough to sustain every single artist, and like a lot of automation advances in the past, it will disenfranchise a rather large population. Besides that, not everyone can just draw furry porn for big commissions.
I think that this should concern a lot of tech persons also who imagine themselves protected from this as the human element of programming, technology design, etc, simply "cannot be replicated", but I think that projects like Co-Pilot are showing that there is a huge focus on replicating AI-Art in the same way, and similar to artists, a lot of programmers are having their code forced into the system to remove their agency, and with no compensation. The very act of producing something in order to sustain one's self is now also an act of self-destruction as the product feeds the AI more data.
I think the technology and the potential benefits of AI generated X is great and it's a step towards removing a lot of the petty grunt-work that is required to make the world work. The big question is how are we going to keep the lights on for people if there isn't a system in place to ensure that people can sustain themselves? Current social safety nets don't cut it, and socially there is still a huge opposition towards creating better safety nets.
I suspect that's why there is such concern over AI-Generated anything; the classic thinking and creative work that was a safe place from automation is now automated, and the world doesn't look ready yet to make the leap to societies that have automated away the need for menial tasks for everyone and provide everyone a pretty nice standard of living.