In Linux you can have as many as you like! As long as you keep thinking that's an advantage Linux is staying in the server room.
I'm with this argument. It's the techie's approach. We can make it customisable, therefore we must make it customisable. It gets to the point where there's too much choice, and people are paralysed in making a decision. So they stick with Windows because it's what they know and it's less confusing.
Sometimes choice is a bad thing. I hate buying toothpaste because it's all powdered rock, fluoride, mint and a binding agent but somehow there are 50 options when I'm in front of the shelf. At that point I take the simplest option. And when it comes to GUIs, for most people the simplest option is to stick with Windows / OS-X.
Pare it down to 6 options that'll work with desktops, servers and laptops. Have an "expert" mode with all the configuration buttons you like, but keep them hidden by default. That is how you'll attract users.
Honestly, for developers they don't seem very good at Keep It Simple, Stupid.
(I think it's been 3 years since I last saw a GUI on a non-Android Linux machine. It used to be my daily driver, and it was definitely viable. Now all my Linux is on the server end.)