As if you don't get a jumble of UI frameworks on Linux too.

You can run KDE but depending on the app and containerization you open you'll get a Qt environment, a Qt environment that doesn't respect the system theme, random GTK apps that don't follow the system theme, random GTK apps that only follow a light/dark mode toggle. The GTK apps render their own window decorations too. Sometimes the cursor will change size and theme depending on the window it's on top of.