I am an example of your philosophy. I’m largely self-taught and agree that the focus should be the points you mentioned. My dad played and that’s how I learned the game, but he never gave me specific instruction on follow through, brush up on ball, low to high, etc. He used a continental grip and I naturally adopted strong Eastern. I naturally developed the correct mechanics from playing and watching tennis, and eventually reached a level that was decent for a “club” player. BUT, I am of the opinion that while technique should not be overly emphasized, players do sometimes develop weird inefficiencies and hitches in their stroke mechanics, and having a good coach who can point out those issues without over-teaching is greatly beneficial to the developing player. At the age of 38, I myself just recently started recording my practices on video, and was able to analyze and make adjustments to my technique that I wasn’t even aware needed adjustment before seeing myself hit the ball. For example, I had always thought my arm was pretty straight when hitting the OHBH, but the video showed I had a tendency to bend it at the end of the follow through. After correcting, my backhand became more consistent. So IMO, both the development of mechanics using the body’s natural intelligence as well as instruction are needed, with the former being prioritized.