I can relate, since I know how it feels not to have enough physical control to achieve what you want to hear from the piano. I am afraid to me it feels you do need to find a different kind of teacher if you want to learn better technique. But that will most likely feel uncomfortable first, both physically and mentally since you might need to break down everything you've learned and build it again.EDIT:If you think building better technique means playing Hanon or something like that, it doesn't necessarily. That can be done just as well by using repertoire and simple studies. It's more about focusing on the way you use your body and play the notes instead of just what notes to play and when. This is what my teacher does. Very little time on our lessons is used on how the piece goes, most of the time is used on what and how I am using my fingers, hands and body, the movements and positions. It's sometimes almost tiresome, because she always finds some new thing that I need to improve when I just got something else fixed...And when I don't seem to be able to improve some part of my structure even with time, she will never let it go but brings it back in another piece...again and again...
My advice:Find a new teacher. I took a couple of years of piano lessons as a high school student and my teacher, in retrospect, I think was more interested in pleasing the parents (look! Susie can play the Star Spangled Banner really loud!) than she was in developing students as true musicians.I can play lots of stuff really loud and fast...but it wasn't until I started working with my current teacher that I realized that I wasn't playing well.If it helps you might look at it this way: You're taking up a slot that could be taken by a student who would benefit and thrive under her guidance. That's just not you anymore.
+1 to bernadette606. There are many different kinds of teachers out there. I thought my teacher before last was good, but my current teacher is far better and I didn't realise that such a difference in teaching skill was possible. Try to get a teacher with a proper teaching diploma, not just a general musican: there are very specific pedagogic skills developed with the former qualification which really do make a difference.To develop the LH, the "Training of the Left Hand" by H Berens is readily available on IMSL and is an indispensable work.