I played Keen exclusively with a joystick for years and was pretty good at it. If you sat me down with the exact same joystick I could probably still play pretty well, but the much looser feel of a modern joystick would screw me up. When my brother and I would play Keen, we'd make the plastic on the joystick case creak from the frantic maneuvering!
Yes, that's the one! You could even screw this little stick into the d-pad and use it like a joystick, or like me, as a child you just broke it off in the hole and never told mom.
https://en.wikipedia.org/wiki/Gravis_PC_GamePad