I personally think three things have driven the degradation in the movie theaters

The lack of competition with theatres as monopolies have formed. This has allowed the average theatre to degrade in quality.

Most major “blockbuster” style movies are designed for the international market. Lots of long action sequences with little dialogue. Simple character development and plots for easier translation. They are all pretty boring.

And last, the improvements and price reduction of TV’s and home sound systems. Combined with the fast release of movies onto streaming platforms or pirate sites.

So what exactly is are theaters selling anymore? A shitty service for a shitty product that is better consumed at home.