Ueshiba left us the good old rowing drill, maybe that's something.
Well, it would be something if people actually understood what Ueshiba's rowing exercise really was, and the actual mechanics of it. Most contemporary aikido would be working in an entirely different way than it currently is.
What most people evidently are practicing these days, is the mimicking of the external appearance of the rowing exercise.
See the thing is, he had ample opportunity to explain it. He either didn't teach it properly, and it's gone, forget it, or he explained it plenty properly and people are, by the by, getting out of it exactly what he had hoped they would. I don't know which is true, but unless you trained under him directly I don't think you know either.