It's not just movies. There has been some interesting writing (none of which I've been able to find with google) about the ways in so many different aspects of western culture (and maybe more) have really gotten stuck for at least 30 years. Hair, fashion, cars, music, food, film, writing and more.
Oh, the claim is not that there are all sort of types of each of these things.
It's that there hasn't been:
1. anything new since sometime in the 1990s
2. any dominant form in any of them since the 1990s
The usual angle is something like: consider hairstyles. Find pictures of popular hairstyles from the 1910s, 1920s, 1930s and so forth, and they will be highly correlated with the decade they were popular in. Now look at hairstyles from the 90s, the aughts, the tens: you will have no idea idea when the hairstyle was popular, because ... it wasn't. In fashion these days, "anything goes", and the same applies to all these other things. At least, that's the claim of this view.
I'm not 100% certain I agree with it, but it does seem to contain a kernel of truth.
That feels like a lot of pressure to put on the 4th film of an action franchise. Might it be possible you could look out of mainstream? There's innovation at the edges.
I'm not sure what was better 20 years ago in terms of mainstream movies. The two biggest films of the year were book adaptions, the next two were CGI cartoons for kids, and the last of the top five was a remake of a movie from the 60s.