Thing is, there are objective metrics about quality. One aspect is "loudness war" aka compression, where subjective loudness gets increased at the cost of dynamic range [1], another (in)famous aspect is the increasing use of auto-tune (both the software itself as well as the general principle after which it was named). Artists and especially producers love that shit because similar to standardization in fast-food it provides a "consistent" performance even in live productions - which is seen as "cheating" in music by older people, and I think for good reason.
On top of that there's an increasing tendency of producers to push for "bland" personalities as well instead of also taking risks, and it's not just music - it's movies as well: most movies aren't original productions any more, a lot of them is based off of prior IP (Harry Potter, MCU) or endless continuations (Star Wars, Star Trek) to recoup ever growing production and marketing costs.