What does Bluetooth have to do with it? First there are lossless Bluetooth codecs and even if you don’t use one of them, good source material still helps. Imagine a jpeg that was resaved multiple times to get an idea how artifacts stack.
Spotify’s codec should in theory even be good enough to not be distinguishable from CD quality, but somehow some songs just sound like shit anyway. I suspect it’s a problem with how they were digitised.
I’m using the free version of tidal instead. In the beginning I had a problem with some things not being on there, but that has mostly been resolved.
I’m also just using Sennheiser momentum true wireless 3. No fancy audiophile equipment.