Much like everything else in the US, products suffer and sink in quality for being sidelined by individual interests.

Marketing needs 4 second jokes to put in the trailer; sales needs a cute pet to sell toys; an actor demands dramatic moments aiming for an Oscar; market research needs a love story, a diverse character, and a specific geographic location to widen the audience; early screenings show that attention drops so story is simplified...

All of these roles should be working to support a product, but they should never interfere with its creation. Instead, they're the main creators. People in the industry genuinely believe that the plot is just an excuse to do all the above, and results show.