Because of Linux's Fragmentation there are so many different UI being created right now and so much more experimentation. There is KDE with endless customization, Gnome for the people who are okay with a more opinionated UI, Cosmic the completely new Desktop Environment and of course the good old lxde. I have to use Windows at work these day and every single one of these makes the Windows feel like it's more suited for Old People because of how slow it can be.
Does KDE have endless customization?
I just installed Plasma with Endevouros and use it. I used Cinnamon before it. They don't require much effort.
Yes but most people just fire up the distro, UI, and settings that they’re most comfortable with for their daily driver. People can and often keep things the same