Maybe Boxing should copy the Tennis ranking system. Each fighter is given points based on who they fight. The higher the points of their opponent will give them a point boost. If they lose to a fighter with low points, their ranking drops significantly. The best one is the one with the most points. IDk but I agree with the useless belts in boxing, its really pointless.
I thought about this too, and I think it has some good ideas. It is similar to Chess with their ELO ratings. But ratings are just that, they are just ratings, and the boxing organizations do that already. ELO ratings or tennis ratings will just rank each boxer more accurately. That is an improvement actually.