> working with complex systems and constraints there often isn't an aha moment

You only get the a-ha moment when there's essentially one discrete piece of information needed to decide between alternatives. That doesn't apply to most problems.

Your brain simultaneously assigns probabilities to possible solutions, and in certain cases there's an information update that sets one solution to probability 1 and the others to 0. If your brain is actively expending energy keeping these possibilities warm simultaneously, then this will naturally lead to a rapid change in energy which will feel like something because it's a change in the flow of neuro chemicals.

It's not obvious that it would feel pleasant. But since the nucleus accumbens is active during problems solving then it's not entirely surprising that the the NAc gets extra stimulated in the rush of energy as the probabilities collapse and weights get updated to the real solution.

But relatively few problems require you to simultaneously juggle multiple possible solutions and pieces of evidence that are brought together in a single instant. So chasing that feeling is generally a poor strategy.

This is what came to mind for me reading the article as well: The difference between juggling, rotating, feeling out a thousand puzzle pieces that either fit or don't fit the well-defined hole you have, versus having the hole, having the puzzle-piece-'blank' that you're very slowly and deliberately chipping away at, sanding down, until it fits(as you know from the very start it will).

One is a trickle, the other a rush.