I think that one reason we worry about dilution of aikido is that we are getting better at it, individually, and it is not as mysterious to us any more. We've passed the stage where we worry about which foot to put forward, when our sensei did things we didn't understand and could neither immitate not resist, to where we are competent martial artists. Of course, we see that there is more to learn, and we want to keep moving forwards, but now we see what sensei is doing, and sometimes he (or she) makes mistakes.
Not that I disagree with a lot of what Stan Pranin wrote. I just think it is partly our perspective that has changed.