I wouldn't be able to use Word attachments (https://www.gnu.org/philosophy/no-word-attachments.html)
I wouldn't be able to use Windows (https://www.gnu.org/philosophy/upgrade-windows.html)
I wouldn't be able to package useful non-free software for my Linux distro (https://www.gnu.org/philosophy/compromise.html)
I would have to call the Linux distro a "GNU/Linux distro" (https://www.gnu.org/gnu/why-gnu-linux.html)
I would have to ideally stop, but at least reduce, my usage of WhatsApp, Facebook, Slack, etc. (https://www.gnu.org/philosophy/saying-no-even-once.html)
These are just all-in-all minor examples I could find in a couple of minutes on gnu.org. I remember reading much more radical takes by Stallman and his companions, but would have to spend more time searching for them.
During the civil rights movement black people were encouraged to not use the buses while segregation was in place. You'd be the guy complaining about how difficult it would be to get around without the bus.
Sometimes the way forward involves going back to fix the wrongs of the past. People like Stallman see the world from a higher dimension. He isn't living on flatland like you and me. There is no world where proprietary software and computing freedom can coexist. If there was you can bet Stallman would be advocating the shortest path to such a world.