Why are we still trying to game theory the votes?

Because that's the smart thing to do when you create an economic system.

We have to accept there will always be side effects we can't predict before implementing the incentive change.

I don't think this is true. The possibility of making a mistake does not mean that mistakes are inevitable. And to the extent that the consequences are not always easy to predict, it still doesn't lead me to the conclusion that changes should not be made. IMO, this is clearly a change for the better.

You don't need to login every 2 hours. As mentioned elsewhere, you just need to find some good posts to vote on that have been posted in the last two hours. Given sufficient quality posts and reasonable tools for helping you find such posts, that shouldn't be too difficult, but to the extent that it is, the people doing such work deserve more rewards.

Content creators in different time zones will lose votes simply because of the time at which they post.

Auto-vote trailing of manual curators will likely negate any impact of that. In fact, it's reasonable to assume that some auto-vote bots would intentionally target posts made during "off hours" for more votes, because they would then benefit from manual voters finding the posts later after the two hour window.