Anecdotal evidence only - so not sure what we can do with it, but I remember when in OS 7 and 8 my Mac ran up weeks of uptime, only being shut down occasionally when I knew I wouldn't use it for longer. Nowadays it is behaving more erratically and restarts seem to improve things.
This is not the idea behind having a Mac.
Even my PC at work can run for a couple of days before it needs a reboot.
I think there ought to be a point at which there is no need for big steps forward(not that there even was any feature in Sierra that I need that Yosemite didn't have), instead, working on stability should become paramount.
I do agree that iTunes is indeed something I find hard to understand. The interface had reached maturity around version 4/5 and every change eversince has only made it more weird. Maybe I'm too old to learn new ways of queing my songs, maybe I have become reactive in not really needing any new way to queue my songs?
It's not the end of the world, but Apple is no longer the reliable option if you want things to work.