It's actually music from an Italian indie rock band, that I previously thought to be badly mastered because it didn't sound the best compressed, now instead it sounds like a breath of fresh air hahah

I also have some classical music in my library, but I still have to properly test it lol, I also expect it to sound much better than the Spotify albums I've heard

Also if what you said about mainstream record labels is true, it's a shame since some of Billie eilish's recordings actually sound so skillfully mixed, I would love to hear more detail in them, even though I feel like they are capable of sounding pretty good even just on Spotify, so I actually agree that it may be as you say