You mentioned 54 year old Shodans and I think it's a real problem if an art does not engage and train younger students. I am always concerned that Aikido maintain a focus on the next generation and not become too absorbed in where we came from.
The 10 years to yondan I mentioned is in traditional training, which is intense. That's not typical for Americans, who are more casual with their training.
I think some arts loosen their testing requirements, but another path is to let students know the truth: their results will correspond to what they put into training!
Iwama is supposed to be harder then aikikai as well. We used to have four days a week of training now we only have two. Its hard to say whats going on. Oh and im not sure how to discuss that young students are few and are between. It possible we just are not compeeting in the market well enough, or even everyone wants to be American national. Champ in the ufc so the take other things.
Hope u answered your question.