Interesting that folks mentioned they can often tell just by looking at someone whether or not they are a good skier. I tend to feel the same way. What is it though? Is it their gear or clothing? Or is it the way they carry themselves or their skis?
IMHO, the better/more proficient you get at something, the less you let snap judgements be the answer. It is a matter of perspective also. One can get a idea about someone elses ability by watching them gear up if you have a lot of experience with various people doing that specific thing. It wont be 100%, but close.
I shoot matches, and compared to the folks that are good in the serious matches, I am a name to fill the lower end. The matches that are more for fun I am normally at the top end. Just shot for my detachment Marine Corps League match having never fired it before, having to change stuff to become compliant, and shooting a position that I havent in 30 years, in a extended time limit that was rough on the knee, I am pretty sure I shot in the top 10, maybe a bit better and I was not happy with the performance dropping points where I had no business dropping points.
For perspective
So as compared to:
National match standards, I suck. Below avg. Make mistakes that cost big time
MC league, I am classed Master
Games matches, I am a Silver and Gold shooter
As compared to the avg guy on the range pre hunting season, I will out shoot every one there most of the time.
Now if I did nothing but the MCL matches, I would think I was pretty darn good. Like bombing Camelback blacks only. Change the game a little and the baseline changes. I saw what the guys in my detachment were doing and knew right then that as a group we were not taking any awards home before a shot was fired. It has to be the same with ski instructors.
As a musician, I find many really good players have beat up and maybe not the best gear but can make it sound great. If someone shows up with a shiny new, expensive drum kit or a bunch of high dollar guitars, etc I am immediately suspicious as I have run across many who suck and just have the $ to buy gear but have not put in the time to hone their skills.
Anything that requires specialized gear is like that. You could put the nicest instrument that money can buy in front of me, it wont help. I have a hard time playing the radio.
Many years ago when I was pretty broke, I bought a rifle to hunt with out of a guys attic for 90 bucks. Cleaned it up, figured out what it was, shot it a lot and took it to the range pre season to test a hunting load. There was a guy to my right and a guy to my left when we got back from hanging targets. The guy on the left saw my 1903 with open sights and started on me how I needed a XXX rifle like his with a XXX scope like his. Think about a contentious gear thread that you HAVE to read because you must be there. Then we started. After I put 3 downrange the guy on the left stopped talking and the guy on the right with a scope looked at me and said "You dont need a scope or a different rifle." I smiled at him and said "I know." I was dead on with a smaller group then the left guy.
Here is a story about George Farr and it is the best example of someone who can using what gear he has.
https://www.ssusa.org/articles/2016/4/21/birth-of-a-legend-the-farr-rifle/
Gear helps. In shooting or skiing, playing music. It isnt the solution to most problems though. A good skier can make mediocre gear preform to the best of its ability. A poor skier isnt good enough to take advantage of the gear to make it worthwhile.