Edit: There's a whole lot of replies trying to sell the idea that AI Slop and pop music is the same. It isn't. You can dislike pop music all you want, you can think it's low effort all you want, but it's not AI Slop. This is a false equivalency.
Personally? I dream of a future where everything is McDonald's. Software, books, articles, artwork, movies, podcasts, music, and basically anything that makes life enjoyable.
Everything will be slop, nothing will be spared. 90% of everything is garbage? That's underachieving, let's improve our slop KPIs next quarter and make Sturgeon's law 100% of everything.
AI slop, Human slop - who cares if people are enjoying it.
Many people do care in fact.
This is obvious, though. This part of human nature will never change, and there is no argument that can confront it, and no reason to want to formulate one unless:
A. It makes you money.
B. It appears to have dividing lines that match a larger culture war in which you have emotional stock.
Your definition of "slop" seems to be "is popular with the mainstream." That isn't the definition used when applied to AI generated music. Spice Girls and Coldplay are leagues beyond anything an AI can currently produce in terms of artistic quality. Yes, there is artistic quality to popular culture.
And to most people it matters that human beings produce it. It may not matter to you - you may only consider music or any other form of art to be nothing more than a means of producing stimuli intended to create a pleasing endorphine response, but most people don't want to process art the way a machine processes data.
I'm being pedantic AF because most people refer to AI slop as "low-quality or careless work". And AI is just a tool so it's possible to spend a lot of time making something of high quality with it. I get the outrage with respect to copyright and artist rights, but it certainly doesn't look like slop to me.