Can you hurt your boxing legacy after accomplishing your goals?

Cut out the RJJ nuthugging. Name any other ATG champion in history that avoided as many top fighters in the divisions they fought in.

This is a touchy subject as you always hear you have to wait until they are retired before you can judge? WHy is this, when what you have done is already in the bag? If you should then lose when you are past your peak its irrelevant. People make excuses for SRL, SRR, Duran, Ali and the list goes on who suffered losses after their best. So why cant people with great resumes be judged now, while they are still fighting rather than when they are retired? People hit RJJ and say he has ruined his legacy? Why?