The desire to help others improve and learn new skills is the essence of being an instructor. Good for you.
I confess that I also find it difficult to watch someone shoot badly without having the urge to coach. That said, unless asked, it's not my business unless it's a safety issue that endangers me or others nearby.
No doubt, in the course of my evolution as a shooter, others have also watched me with horror or amusement.

(Maybe they still do!)
I have, on occasion, struck up a conversation with a fellow shooter and found an opportunity to share info or offer a tip.
Sometimes the fact that
you are shooting well will provide a frame of reference for their level of skill and that will open up a dialogue.
At Front Sight, the instructors step up and shoot a demo on the first morning.
When it's time for the students to shoot, an instructor takes the student's gun and fires one perfect center hit, both to provide a precise aim point for the first drill and to verify that the sights are on.
This immediately removes gun and sight issues as an excuse for poor hits.
A variation on this theme is to comment or ask a question about the struggling shooter's gun and ask if you can shoot it. If you center punch the target you've showed them a higher standard.
At that point it's up to them to choose to seek improvement or to rationalize and accept mediocrity.
Many gun owners honestly "do not know that they do not know". Lord knows we've all been there.
It is kind of scary that a lot of armed citizens have marginal skills, but self defense is an intrinsic right outside of anyone's mandated skills test.
I was once talking to Hock about the sloppy gun handling skills of the average untrained shooter. He said something to the effect that "Yeah, a lot of old time cops and soldiers are a little sloppy with their gunhandling, but somehow they manage to win gunfights anyway."
Kinda put things in perspective for me.
Doesn't make it easier to watch some yahoo who's learned to shoot by watching The Matrix ten times.
But it helps me accept that not every gun owner is willing to (or needs to) train to a master skill level.
Safe gun handling and handspan size groups at realistic gunfight distances are not that high of a standard.
Chuck