So, "everybody is an instructor" is again, one of those phrases that can mean alot of things depending on how you look at it.
You got that right.
In the horse world I often say everyone is a horse trainer. Meaning anyone who interacts with the horse teaches it something. Sometimes what they teach is positive and good, sometimes what they teach is negative and bad. But all are teachers.
The advantage we human learners have over animals is that we can choose who we learn from. Even if someone wishes to impart to us their perceived wisdom it is we who decide whether to accept it and use it or to ignore it and discard it or file it away for future consideration.
I also say, in the horse world, you can learn something from everyone. Even if what you learn is, what not to do.