Something like 4 out of 10 important for me, but 10 out of 10 if I share a computer. I keep xfce4 on my computers because I like some of the utilities that come with it by default and I'm not the only person in my home who logs in. The default setup is close to what my people expect and it can be modified easily enough.

That being typed, I use a window manager after spending years adding custom shortcuts to an increasingly modified xfce setup to match my day-to-day use patterns. I got tired of dealing with stacking windows and wanted to try a setup that tiles the windows instead. It made sense at that time to try out a window manager that came closer to what I was looking for. I still use xfce4 if I want to run an x-11 type of environment for some reason, but I'm using sway for my personal day-to-day environment. I'm willing to use KDE or GNOME if that's what is installed by default, but I'm working against muscle memory when I do so.