These are “desktop environments”. They are essentially the graphical elements you interface with the operating system. icons, windows, buttons, those sort of things.
The two most common are KDE and GNOME. KDE has a very Windows-like appearance and functionality. GNOME is the same but for MacOS.
Fair enough. Certainly some devs spend a ton of time making games look incredible so there’s obviously a bunch of users like me who do appreciate that, and also many who don’t!