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.

Sure but its not baked into the system utilities like in windows.