I do both: stream and play offline stuff. For the former, I use YouTube Music, which is incredibly awful, but at least it does work.
The website version of YouTube Music that I use on the PC is all right, but the app version I use on my phone is a usability mess. Google Music was so much better, but Google has become Microsoft. They're too big to care about making their products good any more.
For offline playing on my computer, I use Winamp. Full stop.