I wrote the book and it is still the bible. The offense adjusts. The triangle is not a pro what the pro coaches understand. They don't have the experience with it. Often they haven't played the game themselves.
Coaches have to teach what they know.
They can't grab something out of the sky. You've obviously seen a number of players who didn't make it to superstardom for one reason or another. It is a question of being in the right place and system at the right time. Much of it is luck. I have seen several that could have been better than they were.