DH

Perhaps it is more fair to his memory to judge, or discuss his teaching abilities from the period when he was actually teaching.

The era in which he actively taught he produced some remarkable men; Inue, Shirata, Mochizuki, Tomiki, Shioda, Hisa etc. These men were pretty substantial in their day.

Retired....has meaning. I don't think it is correct to castigate someone who handed over the reigns to someone else for where the wagon ended up. I also think it is presumptuous to think he should have had the same vested interest. His asking Shirata to "you go help my son, everyone has left the dojo..." at least in part shows his own acknowledgment of a separation of responsibility due to his..."retirement" from regular teaching.
So, on the whole, judgment of his abilities as a "teacher" should be when he was actively doing so. It is documented that he was never a day to day active presence at hombu dojo after he retired.
All the best
Dan