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.
Because art is inherently risky, and the costs for making movies and games has skyrocketed in the last few decades, so the companies are even more risk averse.