I don't know how much of it is there are no new good stories to tell or how much is just it is so expensive to make movies and TV and video games now that the studios only want to go with "safe" properties like franchises. The studios are sitting on entire libraries of unmade scripts that they've bought that will never get made.
As long as humanity continues to exist, there will always be new stories to tell. There is plenty going on outside of the major studios that proves that we're not lacking in good ideas.
I'd wager it's much more to do with the latter, with studios chasing mega blockbuster tentpoles at the expense of the lower budget but more easily profitable ventures that used to be their bread and butter. When a movie has a budget in the hundreds of millions of dollars, you've raised the break-even point to an absurd level that is difficult to reach, and a flop is utterly disastrous. Conversely, if a movie with a lower budget turns out to be a surprise hit, suddenly you've made a pretty tidy profit, but if it flops it's not as big a deal. Blumhouse has pretty much made that their entire model, and it's been working very well for them; doesn't hurt that horror is a steady genre that practically always gets butts in seats.
I'd be remiss if I didn't point out how streaming complicates matters, of course. Back in the day, movies that people took seriously were pretty much entirely made for theatrical release, with "made for TV" being a sign of lower quality. But things slowly started to shift around the turn of the millennium, with prestige TV showing that quality work could be done on television without the format being a negative, especially picking up with the rise of Netflix streaming enabling easy binge watching. And as streaming services began to put out their own original content, productions that would originally have been a theatrical release were finding their way into people's homes instead. That's sucked a lot of oxygen out of the theaters, which are increasingly the domain of the tentpoles and not much else (aside from the aforementioned horror genre).
The short answer is that the industry is complicated, and I'm hardly qualified to untangle the mess that is Hollywood accounting. It would be nice if they'd stop the endless regurgitation of the same shit we've already seen, but outside of a total collapse of the system, I don't really see anything shaking that up.