My son has had excellent pitching coaches throughout this life — mostly through pure dumb luck.
He started playing baseball 20 years ago (he's 23). His first couple of pitching coaches both had played pro ball and I worried they would be too hard on him. I went to all the lessons and sat on a bench a few feet away, never heard a word those guys said because they talked only to my son. But they taught him to pitch, rather than just throw. They worked with him on grips, gave him workouts to develop his lower body (one great lesson was the first guy saying — develop your legs, otherwise you throw just with your arm. That's what I did and that's why I'm here teaching you instead of pitching in the majors).
When the older man died in a car accident, my son cried. After the funeral, he said mom, I feel stupid but he helped me make my fastball work last year. Now I'm taller and I've gained weight and I needed him to help me figure out how to adjust. What am I going to do?
College coaches revamped his motion so that he wouldn't rip his arm off, taught him to use analytics to improve the design of his pitches and to create and master new ones, and that was besides what they did in the dugout during games.
He had two different pitching coaches in college — both are now in the majors, but they still find time to watch his video, offer suggestions and occasionally, just chat.
Good ones, apparently, are gold.