Earlier quoted context omitted.
There are plenty of bots that can play GTO poker better than any human, yet they are consistently losers online at higher levels. Hold 'em, at least, still ain't fully solved.
There are only two ways they can be losers: they are not GTO or the rake is higher than their winnings. Hold’em is pretty much solved (almost because approximations were used for bet sizing). It is possible that you can do better by deviating from GTO to better exploit bad players but that makes you vulnerable to be exploited yourself.
Well, yes, but the point is that a fully GTO non-exploitable strategy is not solved for Hold'em. At least not outside of limit (and kinda no-limit) heads up play.
https://arxiv.org/pdf/1805.08195.pdf
(There is also an argument that Libratus actually just approaches Nash equilibrium and isn't fully there, since there are 1e+160 decision points in a heads up no-limit game, but compared to human players the difference is probably meaningless. )
The closest we have seen for larger games is Pluribus - https://www.science.org/doi/10.1126/science.aay2400 - but the researchers there aren't even attempting to say they have solved 6max, just that they could be less exploitable than some of the best in the world. It is not particularly useful for online play because it does not try to counter variance or manage bankroll, and in further results it began to lose quite heavily as the pros adapted to it, losing 700BB over the 10k hands.
By no means am I saying GTO-based strategy is ineffective - I'd probably be wasting my DTO subscription if I did think so ;) - but we're only part of the way there and the missing bits mean that you can't play perfectly unexploitable poker.