It’d be great if it were that easy, but complications have a way of arising. A cable would be much lighter and simpler than say a rigid truss but it introduces potential problems. At a minimum there probably needs to be shock absorption built into it: you don’t want a “crack the whip” situation, or either Starship swinging or twisting on the cable end. You definitely don’t want random vibrations from the ships to build up resonances. The sort of surprises that the real world loves to throw at engineers. Heck it was only comparatively recently that the Tennis racket theorem - Wikipedia made it’s way into the consciousness of people planning rotating habitats.
ETA: fun discussion, but I think we’ve moved quite a distance away from the OP, which was about the contention that not mastering closed environments here on Earth first meant that the Mars plans were faulty. Maybe a lot of this should be moved to The Great Ongoing Space Exploration Thread