Since the entire thrust of Ueshiba's solo regimen was for building power, since much of his personal demonstrations in latter life involve push tests displays of power you are essentially calling your own founders practices degenerate to his own art. And you don't even understand why or how.
I might be splitting hairs, but couldn't this depend a little on how we look at it? If his overarching goal was to come into accord with kamisama, and this was a way of doing that couldn't we say the building of power was a means to this end? ...That the entire thrust of his actions (which includes the solo regimen) were about realizing a kind of Heaven on Earth?
Might it not be a fair suggestion that O Sensei was more concerned with realizing the purposes of kamisama than of building power? And that this is reflected in how he taught and allowed his students to then teach?