The rider class is in a poor state, I can confirm that after trying it.
The main reason usually named for this is that it is really hard to steer. I’ll describe the issue more concretely and propose a way to fix it.
Motorcycles GLIDE on terrain. They cannot drive uphill and they slide around. Stopping the motorcycle from sliding in a direction other than where the front wheel is pointed will fix the movement issue of the rider class.
Disallowing any sliding basically means 100% traction. It would allow players to actually drive where they want to and through that also set the foundation for using the mounted MG for combat rather than having to dismount and use their own weapons in order to aim correctly.