Some years ago, I broke my collarbone while on a Demo day ski trip put together by a ski shop in Fort Collins, Colorado. Transportation from Fort Collins to Winter Park and back was provided in two very nice chartered buses, complete with multiple video screens.
This trip was popular with the Fort Collins medical community, so on the trip back, the doctors on my bus used the light provided by the video screens to view my X-rays. (Yes, Winter Park has a clinic at the mountain, complete with X-ray capability, as do many large ski resorts.)
Significantly, the two orthopedists on the trip were riding home in the other bus. I had already been informed by the doctor at the ski area that the treatment for this break would most likely be to wear a sling and otherwise leave it alone for six weeks or so to see if it would start to heal without surgical intervention.
After viewing the X-rays, one of the doctors on my bus offered the opinion that I should go to the hospital immediately after returning to Fort Collins to get the broken bone set. I thanked him for his well-informed medical opinion and asked him what his specialty was. "Eye, ear, nose and throat," came the reply.
Upon arriving in Fort Collins, one of the orthopedists from the other bus looked at my X-rays in the headlights of my truck and invited me to visit his office for follow-up. He did not advise me to visit the hospital.
The point? Different experts in a given broad field (e.g., skiing) will have different knowledge, understanding, and experience - and their evaluations will be different. Some may even be poorly informed in another discipline within the same field. Every examiner will be different, and some will be more skilled than others as examiners or teachers or mentors. Some will be dogmatic, some won't. The best you can do is look for what might be useful and thank them for their contribution to your own knowledge, even if that contribution comes with questions and cautions. And you can always ask why. "Why did that trainer say that? Is it just dogma, or is there something I'm missing? If it's dogma, how did it get to be dogma? Why does the dogma (if that's what it is) no longer apply? What has changed? Is my belief possibly my own dogma?" Etc.
Consider, for example, the initial response of many high-level certified instructors to shaped skis, fat skis, and now, early-rise and full reverse camber skis. These "new" developments in equipment are often regarded with a great deal of suspicion, quite contrary to one person's assertion that the purpose of instructors is to sell new skis. After all, these high-level people can ski just fine on the equipment they're on. And, some of them have been burned by GLM and rear-entry boots. Some will resist learning about the new stuff, but other instructors will dive right in. And guess what? Those with the most complete understanding of skiing's fundamentals may find that while some characteristics of the equipment's response has changed, the fundamentals haven't. The skill blend may change, but the skills are the same. Any trained instructor who can ski three feet of powder on a "narrow" all-mountain ski can step onto a pair of Katanas and do just fine. Anyone with solid edging, rotary, pressure control and balance skills can shift from arcing a narrow ski deep under the snow to smearing a big ski near the top of it.
The old-school guy is right, though. You don't "need" shaped skis or fat skis or early-rise skis. And, you can build a house with hand tools. I thought skiing was supposed to be fun. Some enjoy the challenge of the smaller ski, others enjoy the speed and ease of the big one. And if you think the big one is cheating, well, that's religion. (Although we will admit that the big one may allow some less effective movements that the smaller ski would not.)
Does PSIA hold up progress? Maybe some individuals do, for various reasons. In general, the organization and some of its senior people in each division may be a bit conservative. After all, there have been, um, new, New, NEW! developments in equipment over the years that didn't really live up to the hype. Still, many members, including senior and highly credentialed members, welcome new equipment and new ideas if that equipment and ideas can stand up to rigorous testing and application in the field (now do I sound like an engineer?).
Sometimes, a new idea requires some development before it really works. PSIA might be right to let it mature a little. Years ago, I owned a pair of Rossignol Axxioms. 110mm under foot when there were very few such skis on the market. They were great in deep powder, They were pretty good at not breaking through breakable crust. Fortunately, I didn't pay much for them, because under almost any other condition, they were pretty useless. But, they were a start, and today we have much more versatile fat skis, and many instructors ski on them. They still use the same fundamentals, and the best ones stand on their feet and not behind them.
PSIA trainers first taught me to engage an edge and carve an arc before the first "shaped" skis appeared. Shaped skis just made it easier.
I've sitting at a computer, but it sure is handy to know how to type!