The Amazon Music that's included with Prime is bad enough that it sounds noticeably worse than my music from the iTunes store even on Bluetooth earbuds. Free Spotify might be the same.
It doesn’t really matter what you personally use if you’re going to make sweeping generalizations about the quality of streaming music. It’s like saying stainless steel knives are trash just because there exist knives made of tungsten carbide.
I have a 1 terabyte micro SD card in my (2022) phone that holds my entire music collection in flac format. This isn't the early 2000s and storage space hasn't been an issue for years. The only reason I see this not being more common is the mainstream phone manufacturers decided that you didn't need expandable storage and would rather pay an extra $100 for each measly 128gb of storage they care to give you.