Hey, I know exactly what you're talking about & going thru ...I too am 12 years into my aikido training ...I went thru this a couple of years ago, that feeling you're having toward your instructor. I had come to the point of either quitting all together, or finding some way to advance my training beyond what I 'felt' I was getting from my instructor. (...of course all these feelings had to do more with me that what was actually happeneing in the dojo, my instructor had much more to teach me, I just wasn't mentally willing to learn at that point) What I did was turn to an outside source for additional training, something TOTALLY different than aikido ...I went to RMCAT (Rocky Mountain Combat Application Training), the Peyton Quinn camp in Colorado which teaches full speed, full strength attacks against an amoured assailant. I found out that my aikido training was effective, that I could hold my own against an all out attack ...I also found a few shortcomings in my training too ...since I completed that course, I have a completely differnt outlook on my aikido training ...and I've been told by other students and instructors that my aikido has changed since then, it's much stronger, much more efficient ...I haven't 'changed' any of the techniques that I've been taught, the only thing that has changed is my mental outlook, it gave me a 'spark'!
I'm not telling you to go to RMCAT, you might find this 'spark' in some other area, some other art ...take a look around to see what truly interests you ...go do it ...them bring that excitment back to your aikido training!
Best of luck to you!