To be honest, there are probably some people who would prefer the joystick, but then I think others like me who prefer the d-pad. Whatever "action" you have on the input map for moving left and right, it should be as easy as adding "Gamepad Button: D-pad Left" or Right onto the list of accepted inputs for that action. The default UI controls Godot has by default when you start a project actually do this.
This was such a cute game though, thanks for making it :3