> If you want a reasonably efficient market, you need some participants to have close to perfect information.

Is this proven somewhere or you just assume the optimal strategy for markets is continuous?

I mean, it's not clear that the optimal strategy for "slightly imperfect markets" is at all close to the optimal strategy for markets with perfect information. And I actually doubt it can be proven, in the general case.

> If you want a reasonably efficient market, you need some participants to have close to perfect information.

I don't think this follows at all. It isn't clear that if the assumptions are almost true the outcome reasonably close to that if the assumptions were true.

Even if it does hold true remember that economists view monopolies as perfectly efficient solutions but that in that scenario it is efficient because the monopoly captures all the available value not the consumers. I also believe that the maths behind the efficient market hypothesis break down if its assumptions don't hold.