I agree with Marc!
How would you feel in yourself if you were the senpai being discussed?
Personally I would rather be an accomplished 1st dan than a poor 2nd / 3rd dan or appallingly bad 4th dan. Life is not a meritocracy, so why should aikido be any different? All I can do is get up every morning and give it my all to be sure that in the evening I have done my best and leave the rest of the world to do the same.
Enjoy your training, train with guys and girls that don't make you question their ability. Learn some humility, go back train with those that drove you to starting this thread. Rinse and repeat. If you can't avoid these people, just take the medicine and get on with it