I remember one of the first movies to try this was ‘The league of Extraordinary Gentlemen’, I think it was late 90s, early 2000s, Sean Connery was in it as Alan quartermaine They had all these character of popular literature in a shared world, there was Capt nemo with his super advanced nautilus, they had Doreen Gray with his self portrait, the invisible man, Dr. Jekyll/ Hyde, Van Helsings wife as a vampire, and about 5-6 others I cannot recall right now.
It worked pretty good for that movie, but that was sort of a one off film, nothing else was done in this world.
I think they are trying this new stuff because they are just out of ideas when it comes to movies, so if they can re hash a bunch of old ones, bundle some together, create new worlds, etc, its all they are left with. I mean when it comes to movie genres, they have all pretty much been done to death, there is nothing really new to do anymore, I dread to think what it will be like in 20 yrs!