Would it be possible to exploit a GTO poker player if you recognized that you have different values than that player? For instance, if there are decreasing returns to money (such that your first million don’t make as much of a difference to your quality of life as your second million etc). I’m guessing differences of this kind would likely just shift the Nash equilibrium for a particular game but I’m not sure.
I am going to assume this player uses perfect GTO.
The short answer is no. No perfect GTO player is exploitable in any way (that is the definition of GTO). GTO means that the player is making the most optimal decision for long term profit every time.
Most players that play a GTO style tend to be focused on the poker, rather than the money (or other factors outside of the game for that matter). This is especially true at the highest levels (since you mentioned a million dollars in the question). Any player who is factoring in money into their decision making is not playing GTO, and therefore is exploitable.
Hopefully that makes sense, that is how I understand your question.