Actually, I think I've discovered two issues.
The first is that there are too many soft reboots, remakes and re-imaginings. Don't get me wrong, Hollywood has always done remakes and some remakes work very well. The Fly (1986) and The Thing (1982) are actually remakes/re-imaginings of the original 50s films. But they are radically different from the originals and it clearly works having these remakes.
Compare those movies to the endless, mind-numbing procession of remakes and reboots that we get today.
Jurassic Park (1993) was a very successful, decent movie so the big corporation that owns the Jurassic Park franchise thought to themselves, 'let's do that again', so they did. We got Jurassic World (2015). Strictly speaking it's a sequel but its plot is so close to the original film that it can be thought of as a soft reboot. The main difference is that the dinosaur theme park is up and running this time around. Oh, and we also get a stupid, clichéd 'we can use raptors in the military' sub-plot - yippee!
Another example of the soft reboot corporate cash-grab is Star Wars The Force Awakens (2015). It's supposed to be the 7th movie in an already established franchise but it's basically A New Hope (1977) all over again, the differences being it has an altered tone and a stormtrooper who defects (<---- actually quite a good idea but it wasn't particularly well-executed). There's a youtuber named Banditincoporated and he did a full analysis of A New Hope and The Force Awakens, posing the question: if George Lucas took JJ Abrams to court for plagiarism, could Lucas win? https://www.youtube.com/watch?v=Ngg2uBK2j8s
And then there's the shitshow that was Ghostbusters (2016), the remake nobody wanted. I don't think I need say anymore on that embarrassment of a movie.
Think of all the horror classics of the 60s, 70s and 80s. They have all been remade. And the remakes have been mostly pointless.
So, all this and more leads me to conclude that there just aren't many good original ideas floating around Hollywood at the moment.
My second issue is this: I think screenplays aren't well-written nowadays. Decent, well-written characters with decent character development aren't exactly common-place nowadays.
Plots, too, are often substandard. Directors seem to think that if they chuck in a few more explosions then that will cover up their steaming pile of a plot (I'm thinking of you, Rian Johnson). Well, it won't work, at least not for me.