For some material reason, the big chunk of franchises - especially Star Wars, and the one I meatride the most Halo - took a downward spiral in quality starting in the 2010s?
My personal theory is because of the undemocratic nature of big media studios allowing and even encouraging substandard writers to steer them in dangerous directions causing hundreds of hours of talent being wasted.
I think it's the same reason that popular music is so formulaic (This isn't a "modern music bad" argument, this goes for popular radio-hit music of any decade). These big studios are more concerned about making money than putting out a passion project so they go the safe route.