Agree to a point Geoffda, What I have discovered over the years is that to focus on one area and expect good results is insanity. In my opinion there are four primary areas that need to be visited in an ongoing rotation to minimize impediments and optimize skier performance.
Actually I have been brainstorming a good way to present this concept I currently call TAPP which stands for Technique, Alignment, Psychology, Physiology. Isolating and focusing on each of these areas to minimize impediments of poor movements (technique), poor fit, alignment, tuning (alignment or equipment), improper intent to turn & anxiety (psychology), poor fitness, flexibility, symmetry (physiology) will yield the best analysis and plan of attack. As we address and improve each of these four general areas the "skier performance" improves. Using this skier analysis tool we can easily identify weak areas which are the root cause of problems demonstrated by the skier. A skilled instructor/coach can differentiate skier issues into these categories to better pin point the cause of the problem then fix them or refer the skier to a specialist who can offer further help. Each time we address one area it is time to re-evaluate the others to find the next most pressing issue to address and so it goes as the impediments are gradually shaved away to reveal a skier's true potential. Horst Abraham, author of "Skiing Right" said, "learning is taking away, not adding to"
Let's look at a world cup racer for example. Though these elite athletes are in peek condition, with dialed in equipment, strong intents, and flawless technique they constantly work in each of these areas to gain any possible advantage that may still be available to shave off another split second in the race course. If any of these four areas are lacking, performance is sacrificed.
Conversely, look at a typical beginner who comes to the slopes in poorly fitted and tuned rentals, in mediocre physical condition, fearful of the pull of gravity, and no technique savy. The instructor's job is to begin peeling away the layers to reveal a skier in there. The instructor is like your general practitioner physician who job is to do a general assessment of the patient, fix what they can, and send them to a specialist if there are issues beyond his scope and expertise. While most instructors' strongest suit is technique work, the more skilled will identify issues caused by poor fit or alignment and refer the skier to an expert in that field for further help, or identify Physiological issues such as poor flexibility or asymmetric ranges of motion and refer the skier to a physical therapist for functional movement screening and an exercise regiment to address their weaknesses.
So, while many of these forum threads inevitably develop into a montage of advice, I believe the best advice will touch on each area of TAPP and prioritize based on what the skier is demonstrating. Instructors tend to zero in on technique, while boot fitters tend to focus on equipment issues and solutions, Fitness types focus on physio issues, and Psychos on psychos. The ultimate instructor/coach will look at the big picture and evaluate all these areas and formulate the plan of attack!
Another consideration here is looking at how much time and effort it takes to correct each area of TAPP.
Technique takes a long time to perfect
Psychological Intent takes a paradigm shift in thinking which can be an epiphany which happens the first day of skiing or take 30 years to discover, and most never do figure it out (which is sad because this is where the real joy and exhilaration of skiing lives)
Physiological strength, power, symmetry, flexibility takes a long term commitment
Alignment/equipment issues take the least amount of time and effort to optimize in the hands of an expert fitter and yield immediate results in skier performance.
In my humble opinion the first investment of time and money a serious student of the sport or athlete should make is in the area of equipment set up and alignment! because it removes so many impediments to progress. If left unaddressed, compensatory less efficient movements become ingrained in ones technique and consequently make improving performance even more difficult.
Sorry for the rant, but hope this makes some sense to you!?