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.