Your experience and expertise seem trivial to you because you've been living with and accumulating them steadily over a long time.
To someone who wants but doesn't have them, however, they seem impressive.
Think of a young child wondering how adults get so tall.
They may silently wish to grow taller, dismay (erroneously) at how they'll never get that tall, or loudly demand a shortcut (no pun intended) to attaining their desired height.
Short of a miracle, genetic mutation, or painful surgery, they, like you, have to accumulate growth a little at a time.
The good thing is, unlike height, your wisdom can be imparted easily and readily.
You just have to want to enough.
That Spark When Someone "Gets It"
There's something fulfilling about showing someone how to do something, and watching that individual "get it".
Perhaps it's in their eyes, their smile, their general uplifted demeanour when that happens, I'm not sure.
But when you witness it, you know.
And it makes a difference in you, too.
Experts Don't Know Everything. They Just Know A Bit More Than Others.
Being an expert doesn't mean that you know EVERYTHING about a topic. That's impossible.
Rather, you simply have more knowledge and insight on that topic than the average person, because you've spent more resources (time, energy, attention, money, etc.) on it than they have.
That makes you worth learning from if I want to shorten my learning curve.
You spent the resources, so I don't have to.
You Don't Have to Go To Teachers' College To Teach What You Know
Nobody is born knowing how to instruct / teach others.
I suppose that's why there are teachers' colleges and institutes. And, doubtlessly, they produce some excellent educators.
At the same time, most of us won't need to know education history, theory, or philosophy in order to share our know-how with others.
These things certainly have their place and purpose, but they aren't very useful if all I want is to show someone how to do something that I happen to be good at.