there's 50/50 success in using an old version of Google Play Music to play files offline if you're just that used to its UI, and some have a fraction of success in using older versions to stream, but since it's pretty much EOL by Google, that might not last much longer. If anything, it cemented my view against depeding on any of their apps long-term, yes, including Maps and YouTube, as anything they get their hands on dies eventually, and I am of the type who not only tries to buy for life, but keep apps of certain types for life.
I got one tablet, a Galaxy Note 8.0 LTE from 2013, that surprisingly still connects to the online portion of Play Music, since it's showing Roy D Mercer queued up on it, which is a YouTube Music playlist I created some time back, but it no longer gets updates to the OS and Google Play Services so it can't 'force' me to stop using it. Will it last? Nope...probably not. Which is why I don't use it.