End goal is to cripple xfdesktop, just for my user, because it interfers with using i3 as XFCEs window manager.

I've made the script $HOME/bin/xfdesktop that just echos "fuck xfdesktop". A slightly humorous potential solution. The idea is XFCE will execute that instead of /usr/bin/xfdesktop and accomplish nothing. But I'm having trouble getting XFCE to run $HOME/bin/xfdesktop instead of /usr/bin/xfdesktop.

I've tried adding export PATH="$HOME/bin:$PATH" to .bashrc, .bash_profile, .profile, and the XFCE Startup items. echo $PATH shows that /home/user/bin is part of $PATH. I created the script $HOME/bin/bruh that touches $HOME/bruh, just to see if XFCE would execute bruh from $HOME/bin. And it didn't.

If nothing else, how can I cripple xfdesktop just for my user.

Not sure. You could try deleting /usr/bin/xfdesktop, or replacing that with your script. Or try to find from where /usr/bin/xfdesktop is loading and replace that line with yours. Just some thoughts.

Shell initialisation files (.bashrc, etc) are not used during GUI startup. Usually setting variables in ~/.xinitrc works but there are variations e.g. on debian ~./xsessionrc is executed instead. Check what your /etc/X11/Xsession does, user scripts are started from there.

This is what I have in my .bashrc