I don't know jack about ski instruction, or what all the acronyms mean, but my family ski trip last year seems to corroborate that in at least some cases.
My whole family went skiing at Beaver Creek. There were seven of us. My Dad and I went into an advanced lesson, my little sisters in a novice lesson, and my Mom, my brother, and my less-little sister went into intermediate lessons.
My Mom learned to ski during the 80s. She still skis like they did in the 80s. I don't know how this is, I wasn't born then, but whatever they were teaching in the mid-80s in Germany is how she skis. At her lesson last year, the instructor told her to forget everything she knew about skiing and that she needed to start from scratch.
My Mom is a causal skier in her mid-50s who gets out once a year at absolute best (only if I can drag her out with Dad and I). She doesn't want to start from scratch. She just wants to enjoy the mountain, and get a few tips about how to do it a little better. Her instructor was not having that.
So my Mom refuses to take ski lessons anymore. Like I said, I don't know anything about instruction from the other side, so I don't know whether people instructing today even have anything they can do to help people who learned to ski so long ago. But this instructor was very much "my way or the highway," which seems to be what you're complaining about.
That said, I've had more good instructors than bad ones, and I think judging the whole of the community on isolated bad experiences is a mistake. Call out the negative behavior, but don't assume it's everybody. Or even everybody at a particular place. My instructor at Beaver Creek was the best I'd ever had. By the end of day one I was doing things with ease that would've scared me to death at the end of my trip the year before.
Ski technique, for better or for worse, does change as the equipment changes. Skiing used to be "strap your feet to a long wooden plank and put a stick between your legs to use as a rudder". Have fun. That evolved into wedge christies into being about as good as most people could ever hope to get, which evolved into Stein Erickson's style and so on and so forth until we get to the current "style". "Ideal" ski technique will evolve again as ski design continues to change.
The point of modern ski instruction is to use modern gear as efficiently as possible. Skiing modern skis via 1980's-style technique works -- it's just not very efficient. The job of the instructor is to put you on the road; it's the job of the student to follow the road. Perhaps saying "forget everything and start anew" is a little harsh as there are certainly carry-overs, but that doesn't diminish the differences in 80s-vs-modern technique.
This "problem" isn't unique to skiing. I work in the software industry and have essentially learned to write code again several times over the years. When I started, everything was done in assembly language, then we moved to "C", and now to object oriented languages, etc. Programming as it exists today didn't exist when I was in school in the 80s. Johannes Kepler said in the early 1900s that there is nothing new to learn in the field of physics... then Einstein came along and said "everything you know is wrong. Start over".