Not all procedurally generated things are slop, and not all slop are made via procedural generation.

And popularity has nothing to do with private, subjective quality evaluations of the individual (aka, what someone calls slop might be picasso to another), but with objective, public evaluations of the product via purchases.

Procgen has nothing to do with AI in terms of slop, for a good reason: procedural generation algorithms are heavily tuned by authors, exactly to avoid the “dull, unoriginal and repetitive” aspect that AI produces.