As a peer comment mentioned, the wisdom of the crowds only functions when people operate independently. When people collaborate, our answers turn to junk again. And any sort of voting system is an inherent collaboration because you are basically seeing what's 'trending' by definition, so it destroys any sort of wisdom of the masses.

The only way you might have it work is if random people were shown random posts from random topics, and asked to vote on them. And the ranking was based upon that feedback. There's problems there as well, but probably far fewer than in the current system.