Unlike your experience, I am now stuck at high Sierra pretty much forever since this is the last version of macOS to truly support 32-bit. Mojave is a stopgap and nothing more. 32-bit apps are breaking like crazy on Mojave, let alone Catalina. As for the bugs and such, yes, bugs, but not to an extent I want to smash the Mac. Since I also use iTunes 12.6.5.3, I cannot upgrade.
I don’t know what I can do when my current Mac fails. How far virtualisation could help me? Does parallel desktop run high Sierra well? Or at all? I have no idea. Sure, high Sierra runs slow on my Mac. Photos app is still buggy. Mails app takes forever to do anything a bit more serious. But Mojave completely ruins my experience to a point that the only thing my Mac is doing great is booting up macOS fast.
But the main takeaway is: OS upgrade is not really a thing anymore for me in 2019 and beyond. Software will always have security issues. Cellebrite will always find critical bugs that can be used to hack into your iOS device regardless of versions.
High Sierra itself isn’t the best for older apps. Use low Sierra or El Capitan. You’ll have a much better experience with those.
Parallels does run High Sierra, but it’s not great. You wouldn’t want to be using it to play games, for example.