I think that overall, the quality of movies has increasingly relied on CGI and eye-popping effects rather than the master acting, directing and storytelling of the previous generation.
While I would agree in a decline in overall movie quality, I would perhaps offer a different perspective.
First, too many reboots and remakes and retreads and innumerable sequels. How many reboots of the Hulk or Fantastic Four or True Grit or Conan the Barbarian do we need?
Second, too many scripts that are not literature, they are merely action guidelines that result in stunt pay. The plot content of many of the modern action films leaves your head spinning because you THOUGHT that nature abhorred a vacuum. But you found an intellectual vacuum in some of the more modern action films.
I don't mind CGI or practical effects or heavy prosthetic makeup/costuming if the story is any good. Look at the Lord of the Rings trilogy. That was an epic presentation. I shed a few tears in parts. I actually enjoyed the CGI-heavy
Avengers: Infinity War and
Avengers: End Game duo. There is a reason why Marvel has burst on the blockbuster movie scene in the last few years - stories.
I believe that a very large part of the decline of cinema these days is the poor quality of the writing because everyone must think there are no new ideas out there. But students of classic Greek literature know there are only seven basic stories anyway. It isn't the theme that makes a story, its the writer, and I don't see good original screenplays coming out. But the world of comic books and sci-fi novels has led to some really entertaining movies. That is because it used to be that nobody would touch comics as a source because, I guess, they thought that was beneath them. But in the comics, you have stories already scripted and story-boarded. You have back story, you have characters known and loved by a generation of kids who grew up but who are still receptive to memories of comics in their childhood. What's not to like?
The dearth of good stories means diminution of Hollywood output. That's good and bad. Good because it opens the door for "indie" films. Bad because some indie films should have stayed behind that closed door.