I agree, the shell changes are a big step backwards for the sake of some eye candy. Personally I use ExplorerPatcher [1] to restore most of the shell UI back to stock Win10, and it's been working pretty well for me without any problems.
I’ve looked a lot at its source code and it relies on an incredible amount of hackery to actually work. A lot of what it does is injects itself into various parts of the OS and shims in its own behavior. It’ll do things like redirect API calls to older DLLs or even modify data structures on the fly. It’s how it can do all kinds of cool stuff that your typical “Windows tweaked” apps that only rely on registry changes can’t do. (Not surprisingly the kind of things it does can look a lot like malware to heuristic analyzers.) It’s an incredible piece of reverse engineering but it shouldn’t even be necessary to get back such basic things like squared corners and old taskbar behaviors.