It is often difficult for instructors to "pass on the torch" as they have so much emotional investment in the dojo which in many cases they opened.
O Sensei's example is also a probllem in that people often quote his supposedly daily practice until his death at 80+ so they think this is what they should/can do.
My understanding is that actually in his latter years OSensei taught very little - and then only in very short bursts. i don't have an answer but I have often seen this sort of degeneration in dojos and organisations with young (ish) aikidoka ddoing ineffective "old man Aikido" which usually leads to their demise.
You and your senior instructors need to sit and have a serious dscussion about the future of your dojo.
Its a sad situation when that happens and its happening where i am. Believe me. I know of another dojo where i previously before moving where training not onwership was handed off to senior students and yudansa and that dojo is flourishing