> Why can't we peer review this stuff and let the "market" decide what is true.

In a sense we already do. Right-leaning and left-leaning groups already believe mostly non-overlapping sets of “alternative facts”. Each side builds its own narrative not so much because of hate for the other side, but because in aggregate the total amount of misinformation has eroded the potential for credibility of any person or statement that doesn’t come from one’s own “in” group.

In today’s Internet you build your own picture of what’s true. Everything else is noise.