Should I even put fourth the effort?

ever since the fall of 2008 i have been put on this old equitation horse, and at first it was fine because he could jump little jumps. Than transitioning into 2009 in the summer he stopped jumping, so i started working on flexing and suppling. That was fine at the time also. But ever since the end of summer 2009 i have been put on this horse 24/7, occasionally another this horse 24/7, occasionally another horse but once in a blue moon. Now its 2011 and im still being put on him even after i had said i wanna start showing more. Last year i only did like 3 shows and they were flat because im on this old horse. I keep telling my parents that i'm having issues with this, and that it's frustrating. All they say is "well if your miserable than quit" they aren't even willing to meet me in the middle, or help me out in the least bit. I have been putting up with this for 2 years. I have tried to cope through and make the best of it as hard as i can. But if my trainer isn't changing anything and my parents really don't seem like their gonna do anything, is it even worth it. Should i just quit? (Don't get me wrong i love riding thats why ive tried to just deal with this, but it's been too long and im sick of it, i love my barn too because it is the best trainer in my state) changing anything and my parents really don't seem like their gonna do anything, is t even worth it.UPDATE-today I had a lesson and a girl.who leases another horse rode the horse that can jump while I was lessoning than when she was done rode her lease horse, I dont get it. Should i just quit? (Don't get me wrong i love riding thats why ive tried to just deal with this, but it's been too ong and im sick of it, i love my barn too because it is the best trainer in my state)