playing "GTO" doesn't mean you will destroy people, this is a common misunderstanding of the term. It means that you are playing in a way that cannot be exploited - this does not mean you're also playing in the way that will win you the most money.

Also, there is no "better understanding" of GTO because poker is an unsolved game, and the assumptions you feed into a GTO playstyle can change quickly or be wrong. The thought you can sit there like an automaton with a set strategy and win is false.

been playing off and on professionally for 20 years

I suppose I should take your username into account and take you at your word, but wouldn't a player that entirely plays mathematically be easily exploited?

I assumed table talk was at least 10% of poker. Mind games, conditioning your opponent and making reads are present in most sports.

There's a world of a difference between "at the highest level" and your typical casino poker game. (GPs general point still stands.)

This is exactly wrong. At the highest levels you play your opponent, not only GTO. No one can play pure GTO and you exploit how your opponent moves off GTO.

Other than the basics, math is not going to help you win at poker over reading people. The shoot is shuffled after each round, you can’t card count your way to victory. Hand win probabilities are basic math that most poker player just learn instinctively because it’s not that complicated.