You use Gentoo if you want control and transparency. It’s great it if you are the kind of Linux user who wants things in a certain way and wants them to stay that way.
Do you want to use systemd or something else? Do you want to use pulseaudio, some other sound daemon or no sound daemon at all? X11 or Wayland? Emacs built with gtk, some other toolkit or no toolkit at all? Do you care if firefox is built with telemetry support?
If you have no opinion about this sort of stuff or your choices align well enough with a binary distribution then you are probably just as good using something else.