Wouldn't Darwinian processes produce "just barely good enough" solutions? i.e. once you're at the stage where things are good enough to survive long enough to reproduce, evolution doesn't play much of a role.

A great example of this is me; I'm pretty amazing; I can move around my environment, make a living to a sufficient degree to cover costs of food and shelter, and somehow even have a fiancée and manage to keep another organism alive & fed. However I'm not an expert at everything, I'm pretty bad at most sporting based things (even compared to other, existing humans; not some theoretical concept of perfection), and I spend about a third of my life doing nothing (sleeping), despite this not necessarily being required (e.g. Dolphins can sleep half their brain at a time, allowing them to avoid this inefficient downtime).

Yup. Until there's selection pressure working against you once again. Imagine if society broke down completely, so you had to fight for the limited amount of food that was available?

Somewhat related: it was interesting when my kids were born; they both had to be C-sectioned. I asked the obstetrician about it, and yes, bigger heads are becoming more and more common because mother+child no longer just die when they do occur. We really are removing selection pressures!

That's a nice way to put it. My personal opinion is that Darwinian processes are certainly optimization algorithms, they are just not necessarily optimizing for the same thing as what we might think. As an example, survival is a long-term game. I'm sure there were more aggressive adaptation strategies that went for the local minima and succeeded in the short term, only to be surpassed by the more "patient" algorithms.

There's a huge difference between "exploit in the now" and "exploit, but still be viable in a billion+ years".

A great example of this is a virus which is optimized to spread so quickly and aggressively that it extincts itself by wiping out its available hosts.

The Greedy algorithm at work.