Don’t feel bad, frankly they didn’t ask or care about what the user userbase thought. Even many of the vocal of us found out after the fact.
For what it’s worth I import all my local files into Apple’s Music App on my main Mac and then copy these to a dedicated Roon Core/Server for preferred use.
In the event of Internet outage, the Apple Music App continues to play local files just fine. Sad but it works.
This is what I call a “work around” but it sure ain’t a “fix”.