The thing that you're forgetting is that the big studios aren't in the business of making good movies, they're in the business of making money. So if they release a film that some consider garbage but is a box office hit then they're happy. Now, if a movie is both a critical and box office success, so much the better, but it's hardly a requirement. To most studios, I don't even think that an Oscar or a nomination means much except as something to add to their marketing campaign to increase ticket sales.
Something else to bear in mind is that your big tent pole movies are no longer being aimed purely at the domestic US market, or even the Western market, these days. Something that's a flop or just modest success here could be a huge hit overseas and for a movie to be successful overseas, particularly in Asia/China, the story has to be simple enough that it works no matter the language or culture. It's also part of the reason why remakes & reboots are so popular, we've seen these movies before here in the US, and Europe, but in other parts of the world they've never seen the originals before, so, for them, it's something new and never seen before.
I do understand that moviemakers are for profit, that they will generally do what is least expensive, requires the least effort and is the safest for maximizing sales in the all of the international markets they are in. They will do this as long as it is profitable. As complex as the industry is it still comes down to the fact that it is business. If consumers, wherever they may be, continue to support the industry's unimaginative repackaged formulaic movies en masse it will continue to make them and the bar will remain low.
Perhaps with the momentum shifting towards niche markets the film industry will make movies that appeal to smaller markets more than attempting mass appeal with every release.