If you make it to the psychology section, that's where the explanatory power becomes apparent (or at least is speculated on). Though, yes, it is a lot of text to get there (I'm relieved that some people made it that far).

If you do make it that far, there is a payoff, though. This "trivial kind of system" isn't merely an analogy but the actual algorithm that we use, and the "implementation details" of this algorithm manifest in unintuitive ways that have a lot to say about how psychology is understood in general. Though, given your skepticism, more research will likely have to be done before this is satisfactorily proven to you.

This breakthrough (which I'd say is primarily K&A's breakthrough that I merely am speculating on top of), is actually a great example of theoretical progress. I typically consider myself an anti-reductionist, but this is a lesson in how studying simple systems (in this case, chemotaxis), can lead to better understanding of complex systems (because, well, it turns out at least in this case that these complex systems are actually the same simple systems at the top level—the complexity gets added in "layers" much like the evolution of brains).