Can you explain why?
From my understanding playing a gto strategy would mean that you bet, raise and fold at certain frequencies independent of players in the game and the strategy would never need to deviate. In situation X the option would always be Y. So you are always breaking even because the strategy is unexoloitable but when another player makes a mistake by not folding to a bet when you have a made hand for example, that player has just freely given away money causing profit.
The strategy isn't about breaking even, it's about being in unexploitable. So if multiple players use this strategy you will break even against each other but anyone who doesn't use this strategy are now exploitable and will lose money due to making mistakes.
A GTO strategy is basically playing all situations according to Nash equilibrium, which, by definition makes your opponent indifferent to changing his strategy. In poker terms, that means putting your opponent in a 0 EV situation always. If you play GTO in a particular situation, it doesn't matter if he folds, calls or raises. Whatever he does, his expectation will be 0 EV.
So by definition, he cannot make a "mistake" against you, and you cannot profit no matter what he does.
And by the same logic, you cannot both be unexploitable
and potentially profit from mistakes. Because if you want to profit from mistakes, you must deviate from a GTO strategy. But if you deviate from a GTO strategy, you are by definition exploitable because the opponent can change his strategy to potentially exploit whatever imbalance you introduced to yours.
Another point is that in poker, a GTO strategy is always dependent on your opponent. It's different from a game like rock-paper-scissors because in poker the potential ranges of your opponent are clearly changing from situation to situation. For example if you are on the river and you want to bluff 30% of the time, value-bet 50% and check to lose 20% of the time, you need to set up your ranges in advance such that you actually win every time you value bet, lose every time you bluff/check. In order to achieve that, you have to know the exact range of your opponent in that situation, which, in turn depends on his frequencies on turn and so on. It is impossible to play GTO in isolation from your opponents.