At the species level the nature couldn't care less about a single specimen. If you have offspring, suffer as much as you want. If not, too. Suffer anyway, just leave offspring. Or not, who cares.

Professional therapy (at least the one I experienced) uses well-defined methods in addition to drawing parallels and analogies. Downward arrow, event/emotion logging, exposure, core belief removal methods, etc. I was really intrigued when I realized that therapy is not about whining and listening to "it's okay" or shallow advices, but akin to debugging and programming with a mentor who already seen most bug like yours and only needs you to start dumping logs to confirm.

You can come up with something vaguely like this by accident, after talking to lots of friends. But why bother if you have a professional who can point out the inconsistency and suggest/explain the way to solve it in just in a few sessions?

I'd say people for a long time, in many cultures have gone to trusted faith leaders or elders to seek guidance their peers weren't suited/equipped to give.

Those harder times that caused more trauma were themselves almost always caused by traumatized people who had no way of getting help. Friend/family support systems rely on people actually knowing what to do, and most have no clue whatsoever. The treatment for "shell shock" was to man up, and "hysteria" got you an ice pick to the brain.

Evolution works on the scale of millennia, we've been the same organism for the past 300k years and it's random best effort that only selects based on what kills you before you procreate, it doesn't guarantee anything at all.

Neither one can still substitute for the immersively subjective realities in which our psyches were formed around, nor even begin to answer how that relates to everything we pick up and carry throughout our lives. Perhaps it would take an equally intense experience, developed over a lifetime and coupled with accurate insights into how those relate to the brain, to change some deep-seated traits or begin to answer how something such as a disorder actually behaves in the brain.