IMO, the benefits of an immutable OS install outweigh being able to uninstall/remove particular apps.
Apple makes excellent hardware (laptop, phone, mini...) to the point I'm willing to pay more for it, but I would prefer a lot to customize my SW. And so I avoid their hardware.
do the benefits of a closed-source OS outweigh being able to do whatever you want?
You cannot uninstall Music.app indeed. There is one toggle that hides all of Apple Music. It completely hides it, to the point that a link online to the service will error out.