This statement makes no sense.
I think the statement makes perfect sense. You could have learned to dive in a very slow, methodical, and skill-refining approach. You could have been exposed to excellent instructors along the way as you got certified to higher and higher levels of diving. You could have been introduced to highly effective teaching methods because your instructors used those teaching methods to instruct you and help you develop a high level of skill and deeper knowledge than many instructors impart. Perhaps you are even a teaching/training professional outside of diving and so you have a sound understanding of what is involved in teaching/training people on new tasks. Because you're a passionate diver, and passionate about teaching, you want to bring your professional knowledge to bear on your hobby.
I'm not talking about me necessarily, just saying that it could be the case. But I think you are unable to accept that someone who matches the description above in pursuit of their dive training could even consider a quick/cheap course to become an instructor because that would seem to violate the value they put in methodical and thorough instruction. However, I don't see these as antithetical at all. Certification agencies have a relatively fixed, modular curriculum for instructors to follow. The instructor is potentially much more qualified, from a diving perspective, than the material she is instructing (e.g., a technical diver teaching an OW class). I don't see why this person should be considered inferior because she pursued a cost effective, time efficient approach that met the standards of the agency that certified her.
Students learn best by mimicking, right? An instructor with poor trim and buoyancy control can't hope to teach it, since the student has no credible reference to imitate. They will probably look just like their instructor and if they become an instructor, they will pass that on to their students as well. It's the circle of mediocrity or the circle of excellence. Choose well.
So...this is a skills issue, and it seems like you're saying all an instructor needs is to have good trim to teach a student good trim because a student learns best by mimicry. That would mean that teaching methodology is irrelevant for this (and potentially other) skill(s). Is that what you're saying?
When you are in an IDC, you are learning how teach. Just like an OW student, you will imitate how your instructors do it.
I think you're making a LOT of assumptions with this paragraph. What if an instructor candidate determines that their IT is not that good. They are potentially qualified to make that determination having seen many other instructors from different agencies in the past, both as part of their personal dive training and during recreational diving. Obviously an instructor candidate that thinks their IT uses inferior methods isn't going to mimic those techniques. I wouldn't see anything wrong an instructor candidate continuing on through the course, meeting agency standards, and becoming a certified instructor though. They could walk away from the IDC saying, "I now understand the philosophy and methodology used by my agency in certifying divers and I understand where I can use my own teaching methods to improve outcomes, namely the skill and knowledge of the divers I certify."
I also don't think you're giving people enough credit for being able to think for themselves. You assume that just because someone has an impatient instructor they will become one too. That doesn't make any sense to me. If you're an impatient person, teaching...anything...is probably not the right job for you. If scuba is your hobby and you are considering teaching it to others, but know that you're really impatient, then I don't know how you would arrive at a decision where actually becoming an instructor made sense. It is almost as though you are saying that people are so impressionable, and so zeroed in on a single source for all their information and knowledge, that they will invariably become an example of that source. This certainly could be (and probably is) the case for many. But it isn't preordained, and isn't the case for all--just look at the numbers of people coming to Scubaboard to ask questions and get information. For instructors, a little scrolling back through threads and you see many, many instructors indicate that they teach above the minimum standards. So clearly, people considering becoming instructors can think for themselves and do not have to perpetuate the things they saw as negative in their training.