Yeah people seem to forget that before AI music, there was already a huge amount of "slop" music out there - background music, muzak, mood music. Hell, Spotify was put in the spotlight not that long ago for commissioning music to mix into their own most popular mixes (the casual background listening ones), so that they own the rights themselves and don't need to pay artists as much. A lot of music is for mass consumption / inactive listening, and honestly I don't think it makes much of a difference whether it's AI generated or churned out by a WFH producer. When it comes to whether I want to listen to it anyway, not so much whether said producer gets paid.
None of that is what I would call slop music. All of that is real music for real people with real use case.
Also the almost industrial score music machines: trailer music, like two steps from hell, even Zimmer. Those are also can be considered as slop, even worse - highly formulaic, almost standard (YouTube “heroic music chord progression”). And those were written by humans