Websites like Reddit definitely have great content, but as parent commenter pointed out, this content is necessarily the kind of content that appeals to the average user, and there is no room for outliers.
I think the Amazon model for deciding is still a better sample of an audience than a bunch of grey-haired men sitting around a board-room table whose first question is "will this be profitable?"
Hint: Unsubscribe from any sub-reddit that new users default to being subscribed to...
The conflict between art and craft is present in almost every kind of media, in my opinion: Whether it's books, music, or movies. The only difference is that some media are cheaper to produce and thus more open to art.
The higher the up-front costs for a medium, the less room for art. If it isn't resolved on the script level, it will get punished at the box office.
I assume, this is what worries Amazon, too: Writers who think of themselves as artists are probably those who are unlikely to sell their script(s); but they are also the ones desperate enough to submit it to Amazon. There might be a nice idea in some of these scripts, but they probably need some additional work.
Of course, a bunch of guys who have no clue about art or craft aren't going to produce anything worthwhile, no matter how many of them participate.