Humans are in a very different situation than they were for most of their evolutionary lifespan.
For one: there is an abundance of resources: tweaks that increase brainpower at the cost of calories which might kill on the Savannah would be solid gold by today's standards. You'd be smarter AND hotter!
For two: the kind of things we want people to use their brainpower on are not the same things the brain was evolved to optimize to think about. For example, despite being dis-tractable, my girlfriend can concentrate on and pay attention to animals for hours, and has a strong desire to walk miles and miles every day. I'm sure this was very handy for persistence hunting, but it's a handicap when it comes to working in a bank. And so Vyvanse comes to the rescue: not as a PURE nootropic but one that allows us to make different neural tradeoffs than evolution was interested in.
For three: Human intelligence already varies quite a bit, much of it achieved by 'tweaking' a few chemicals (DNA, for one). We don't understand the neurological difference between John Von Neumann and an average person, but I think there's a decent chance that within that variation is not just genetic/developmental differences but ones in neurochemistry that can be duplicated in others.
Finally: evolution is incapable of exploring chemical-space by more than a few compounds per generation. Despite their utility, humans never naturally evolved to produce penicillin, or caffeine, or opiates when needed. There is a HUGE population of chemicals that the human body has never tried producing which we can utilize. The argument that "If this was possible, evolution would have done it" proves far too much.
So Scott Alexander's post at http://slatestarcodex.com/2016/03/01/2016-nootropics-survey-results/ shows that the most "effective" "nootropics" have still been the ones that have existed for a long time. What do these results really mean, though? Is it possible that people are just worse at noticing the subtler effects of the other drugs, or are just much worse at disciplining themselves enough to correctly use the racetams or noopept (as in, with choline)?
How much potential is there in innovation in nootropics? What is holding this innovation back, if anything? It feels like there hasn't been any real progress over the last 15 years (other than massively increased awareness), but could targeted drug discovery (along with people willing to be super-liberal with their experimentation) finally lead to some real breakthroughs?