I haven't read all the posts in this thread, so forgive me if you have said this before. Let's take the instructor out of the picture for a moment and focus on the concept of the training and the system. Now, I doubt you'll find anyone who will say that changing a system to make it "better" is a bad thing. What we should decide is whether the FTF is improving on the current training of traditional TKD, and in my humble opinion, it doesn't. For this, I'm going to refer to this video from the FTF website:
Throughout the video there appears to be a lack of focus on the intent of the training, which could get very confusing for newcomers. We start off by hearing that the FTF focuses on self-defence, whereas "traditional" TKD focuses on forms, and we get the usual misrepresentation of forms as a training method. Ok, you don't want to do forms in your system? Fine, there are plenty of systems that don't use forms and are perfectly fine. He also wants to focus on self-defence, which again is fine. But here's where the problems start. He says (and I quote) "We teach you combat sports".......So are we learning sport fighting or self-defence? Then it gets weirder. He says "we teach you boxing, muay thai and Olympic-style Taekwondo".........huh? You say you want to teach techniques that can be transfered to street fighting/self-defence and yet you do Olympic-style Taekwondo, which is about the least realistic modern fighting sport you can get.
So, are they training for Olympic-style Taekwondo competition or self-defence?