Can you name any human activity where students can effectively learn by turning up to lessons sporadically, run by different teachers, with totally different fellow students, with a random learning environment, and where student spend most of the time between lessons re-enforcing bad habits?
I think I actually can.
How about martial arts ? Instructors can rotate, but still teach same movement patterns and same fundamentals. It's not a way to become a professional MMA fighter, but there is certain level of consistency that allows students to progress from beginner levels without feeling constantly confused.
Or yoga, People learn movement patterns in a group setting with different instructors on Mondays and Wednesdays and yet feel like they are taught the same thing.
The tricky part is re-enforcement of bad habits between the lessons. Unfortunately, in all my time taking group lessons I've never heard a ski instructor say "beware that going on the steeps will wake up your bad habits. I know that steeps are more fun, but try to make sure to spend half of the time enjoying the greens. This is where you can solidify the skills we learned today".
@abcd have you considered ski camps as a way to obtain more consistent feedback in a forum where you have several days to work on it?
Yes, working with the same instructor during the season and taking camps several times a year now.
I also took a group lessons this season, I was bundled together with 3 students who wanted to ski steep greens and blues. I was told to push with my new outside foot to start the turn and to stand up tall in between the turns. Exactly same things I was taught when I started and that I recently spent 4 years trying to replace with new movement patterns (not very successfully). The other 3 students were very happy with what they have learned and commented how useful the lesson was.