Yes.
And that's because GOTG Vol. 2 is such a weird movie compared to all those other franchises. It's not conventional. I can't remember a movie as weird and crazy as this one having such a big success. Even the first GOTG is way more conventional.
If we look all the biggest box offices of all time, we can see:
- Every movie that made a billion or more (or even more than $ 800 M) has a much more common, familiar plot and/or a much more conventional way to tell/show the story.
- Most of these movies are also more grounded, with characters and places that are either on Earth or look a lot more like Earth.
- They also have a much more global cultural approach; GOTG Vol 2 is much more connected to American culture (in references, songs, style and even jokes) than all those other movies.
Plus, Space Operas (and Space Movies overall) aren't that big with foreign audiences. Even 'Rogue One', with the 'Star Wars' brand, after the HUGE 'The Force Awakens' success and with a very good critical reception, made less money OS than 'Batman v Superman'.
I think, looking to all this history, people were expecting too much from GOTG VOL. 2; The film is a big hit, but it's not the kind of movie to make a billion.
At least not yet.