Matt Damon talked about this somewhere. The risk aversion stems from the move away from DVD sales. Historically a lot of low and mid budget movies relied on DVD sales to recoup costs even if theater releases didn’t get you as much money as you expected. With the safety net gone, studios don’t want to take the risk. They make big budget movies with massive marketing budgets that rely on known IP and established fan bases to guarantee income. This also ensures that the story itself is average because you want an average fan to like it.

I think calculus somewhere has changed that is allowing these small/mid sized movies to be made again.