Haha, well it's not only X11, but it's one of the main reasons. Other reasons are that for my usage and work, it just "works", no hours of configuration in dotfiles. Also it's convenient as a cross platform developer, since I can just crosscompile to Linux and Windows(mingw) via Docker. However, without the Mac, you'll have to break some licenses with a hackintosh. I think the project is cool, but in work related situations I can't do that because of legal reasons.
Yea personally I'm mostly fascinated with the semi microkernel architecture. I don't really mind that the rest is closed. And yea, I've suspected they lost some good people after seeing all the new security issues in the kernel the past years.
If only wayland was more mature, and the Linux world would have put down X11 once and for all, I would be back on Linux a long time ago :)