Ack! Where to begin? How about here: "It only produces the best solution possible within the range of variability that exists." - Isn't that the very definition of optimal? Unless conditions have changed evolution *has* found the best solution and we should be very cautious about thinking we can improve on it. I'd accept that road walking/running is a change in conditions because those are man made surfaces that we didn't evolve with. But certainly for trail walking I don't think we face anything our ancestors didn't.
Ack, ack! I don't think you understand evolution. Evolution is the process by which variants are selected for their effects on fitness. Evolution only produces the best solution among the alternatives that it has to choose from. This isn't optimal--it's just the best of whatever different kinds of variants exist in a population. As a result, many aspects of the human body are decidedly non-optimal! We choke easily, our teeth are awful, ditto for our backs, etc. etc.
The bottom line is that just because we didn't evolve with cushioned shoes does not make them automatically worse. We didn't evolve with fluoride toothpaste, but lord knows that our teeth do better with it than what our ancestors did--pick at their teeth with pieces of bone. Human bodies are not optimal--in many ways, we do better doing things differently than we did 100,000 years ago.
FWIW, I'm not arguing that cushioned shoes are better! Just that you can't know if they're better without actually testing them. Evolution can't help you answer that question.