Like, if Mongo is mispriced relative to Amazon, and you confidently see it, you will trade accordingly and erase the price difference.
In what I recall from my CFA studies, research shows that only genuine insider information can consistent outperform the assumption that all information is already priced in.
And for example, let's say you perceive Amazon and Mongo as mispriced, but what if that's because some even bigger expert than you saw something you didn't and traded accordingly?
(For what it's worth, I used to work for one of the world's most significant hedge funds. Our win/loss rate on trades was something like 52/48. So even as literally the worlds top investors who spent more effort, brainpower and money to gain insight, we were right just a bit over half the time. It really drew the point home that a random non-insider individual who thinks can do that over decades is likely delusional)