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.
Innovations in capitalism get milked till they run dry, almost always at the people who made the orginal IPs expense.