That is usually the best advice an arborist can usually give unless a tree truly has a significant defect.
Let me start with trees, Leave them alone.
That is far too negative a view. As an arborist, you are supposed to have technical knowledge on how a tree will respond to what you do and utilize that knowledge in your work. If all you see or can predict are negative responses, you are doing it wrong. That is not the same thing as saying that it can't be done correctly and in a manner that benefits the tree, it is merely saying you either don't care or don't know what you are doing.
I do have a negative view of most of our industry like most "industries". Our capitalist society and our place in it means that many arborists are less than ethical in their recommendations for trees and for what trees "need" as far as redirection of growth.
Most of the time yes I can look at a tree and see a few key cuts that could be made that would slightly or occasionally significantly benefit the long term structure of a tree.
But as a contract climber quite often I am put on jobs where trees that have no significant structural defects are listed on the quote as needing "pruning". I usually joke with the crew about being paid by the pound and go for a rec climb up the tree. Perhaps I make a few cuts that are necessary and at times feel the need to take out more to take up time or to put brush on the ground so the customer can see that something was done to their tree to justify the charge. The new cut facing the kitchen window is always best practice right? I think Gilman included that in his latest book.
My point being that I, a Treebuzz aficionado who has been in the industry for 23 years at times feels confused by the blanket statement of "pruning". This is usually on a jobsite with a crew needing hours, a truck and chipper needing payments, and a customer needing their tree to have "work done" are all looking at me the expert. What does the new guy with no education do? They gut the tree. They over reduce the canopy. They over elevate. They take the paid by the pound concept to the extreme.
My solution? More education of the customer, and setting the bar higher for licensure to enter the industry. For there to be zero educational requirements in most states to start or participate in our "industry" is laughable and makes us the last thing anyone would consider a trade. Changing that would be a heck of a start.
I am will a sizable company that is preservation minded and we get enough unethical work as it is. Our area is scenic so we find ourselves on some pretty destructive view projects that always bother us.
Sorry man, but asking others to change what they do, when you, with all your moral convictions and knowledge are having trouble with this, how will more education help?
If people with the knowledge, can't/won't/don't live by a knowledge-based code of conduct, why should others be expected to. It is not just what you know, it is what you do with that knowledge that matters.