It happens. I'm out doing something or whatever, and some well-meaning asshat will offer me advice. Here is a list of the random advice I get from people who are not coaches:
"You should try holding your arms on a table," they smile and exemplify the move. Then they skate off like a mannikin, looking back at me to make sure I'm trying it. I'm not.
"You need to hold the undercut," they perform the back crossover with a rapid fire push and a super elongated hold and a toepick that can be heard in the lobby, while looking down.
"You need to bend your knees." They do a squat for you to show you how to bend your knees, as if you weren't aware, but then skate away with forward strokes on chopstick legs. With the "arms on a table" position.
"You need to stop scratching." These words are usually not followed by an example, because they scratch to high heaven. They know this, and will usually blame their blades because they are better blades than yours.
"You need to stop looking down." They then do some basic skating showing you how to look up and smile, but the moment they do a power 3, they are looking down and hunched over to inspect their tracings.
Listening to such advice and then watching these people skate usually elicits this response from me.
Why do these people feel qualified to offer such fabulous advice?
They have been skating a long time.
Yes, I understand this. But you can run in a hamster wheel for fifteen years and still be in the same place. I can understand if they are actively training and working, but when I've seen them do the same set of skating tricks for the past five years with not much advancement, I have to hesitate.
They have had "a lot" of coaches.
I actually do not consider this a badge of honor.
They have skills you do not.
It's true, I can't do a salchow and my spin is not quite there yet. I've chosen to focus on building a strong foundation before pushing to do higher level skills that may look awkward and forced. It's a difference of focus, opinion and personality. Simply possessing a higher level skill does not give anyone free license to critique someone else's crossovers. Besides, if you pay attention, you might find you do some "lower level" skills way better than they do.
So, what do you do?
In most cases I will smile and nod politely, and go my own way, doing what my Coach has told me to do.
In other cases, where my refusal to do things their way becomes an accusation that I "can't really skate," I resist the impulse to jam the back of my blade into their orbital socket and calmly explain that my Coach has given me a different way and that is what I will do.
The most competent adult skaters I know do not offer unsolicited advice. They may offer generalized words of wisdom such as "Practice" and "You'll get there," or general encouragement, but that's all. They work on themselves and let others do likewise.