A window manager is part of what you use, unless you run one program in its dedicated X session or don't use X at all, or use Wayland, in which case you use a Wayland compositor.
If by "window manager" you mean only standalone window managers that are not part of KDE or Gnome - then just as usable as those that are.
If you mean that catching someone with a terminal emulator open disqualifies its author as a showoff - many of us actually do use CLI and TUI programs, and for that we need terminal emulators.
If you think that "window manager" means only tiling WMs from r/unixporn on Reddit - the choice is kinda bigger, there are a few hundreds of them.