In theory, I understand why GTO should work and what makes it a smart idea. But in practice, it seems like mostly a gimmick to make people think they can master poker solo, using books and software, without significant experience at the table with the wide variety of players who populate the game.
If the strategy is truly GTO, it shouldn't matter if you're calling the river a lot and losing. Long-term, your opponents shouldn't be able to counter a truly GTO strategy. But it sure sounds like they are leaving it in the dust, at least on the last bet. Even adjusting for the tendencies of an entire pool of anonymized players is playing exploitative poker, so if you're doing that, you're kinda admitting defeat on the GTO front.