I think it's more the former than the latter. The cost of Indiana Jones shouldn't be 300 million. That's just ridiculous. It makes the uphill climb even greater. I'll agree that the original stories aren't as good as previously done but I feel audience are too tied up in nostalgia to opt for original stories now. We appear to only want sequels. Marvel is going to have an impossible time topping Endgame, something built towards for over 10 years. Now it's left with just a few of those characters and audiences may simply be tired of seeing superhero movies. It's fitting that Guardians 3 is the top movie of the summer but even that wasn't considered a true blockbuster. It was the final gasp of Endgame characters.
I don't think it's just that Disney isn't telling great stories. I think conditioning your audience for over 2 years to rely on
Disney+ for content had huge detrimental effects. I still haven't seen Elemental and may just wait till it comes out on Disney+. There's lots of other movies on our plate to see first since they have a finite shelf-life before I can see them in my home.
The only blockbuster of the summer might be Mission Impossible which I think will pull in a lot of the Top Gun crowd.