A lousy Instrument instructor was one of the best things to happen to me. I had no right to take my checkride based on my level of knowledge. I vowed that I would never show up to a checkride unprepared ever again. And you know what? I didn't. Good instructors, bad instructors, and indifferent instructors have been a part of my training ever since, but I realized the final say in my level of preparation was me. I will say, that is a difficult thing to ascertain as a Private student. A couple more ratings under your belt and you should have your instructors figured out pretty quickly.
Like several other posters have stated, there's a lot of other options out there, and you're the customer. All the best, and hopefully you can figure out what it's going to take to get you through training.