What a topic!
In Aikido, and other traditional martial arts, you are likely to hear that everything has gone downhill since the Founder, since the Founder could rightfully be said to be the only one who practiced the art in its' "purest" form. However, this is not true neither is it historically valid.
Jigoro Kano is the "Father" of Judo. yet many of his direct students were much better technically than he. His particular strength lay in his ability to put the system together in the first place.
Morihei Ueshiba has been described as a "physical genius", that is someone who seemed to understand spritual and philosophical principles with his body. This led to his rather unique ability to literally "embody" his understanding.
What has happened is that standards have changed. Most Aikido organizations now have stated requirements for the various ranks, usually with some minimum number of hours of training. I remember being told that I was going to test no more than a week out from my exam. There did not seem to be any minimum, as my Sensei at that time would simply decide the you were ready for the next rank based on how well you were doing in class.
Presently, Seidokan has stated minimums for all ranks. While this does not "guarantee" quality, it does set the baseline for the student.
Quite frankly, I have trained with top ranked instructors from the "old days" and while they were impressive to watch, as "teachers" I have seen much better.
For me the "standards" are up to Aikidoka. a truly committed student can always surpass their instructor, and should. The instructor should always challenge their students within the student's abilities.
"Do not worry about people not knowing your ability, but worry that you have not got it."