But frankly, none of the Jurassic Park movies did that anyway. The movies have always been about the dinosaurs.
That's absolutely true but at least there were familiar, recognizable faces in the first Jurassic Park like Goldblum,Attenborough, Laura Dern, Sam Neill, etc. Nobody who would sell tickets by themselves but at least provide some veteran support to the story so it wasn't entirely being carried by FX. Certainly more recognizable than this movie, which has a cast that is almost no-name across the board for the large majority of viewers out there (I'm not sure anyone has ever cared about Bryce Dallas Howard's career, but she's essentially the biggest name attached -- and that doesn't say much, obviously -- with the exception of the actor you're not mentioning lol).
They are absolutely banking on the dinosaurs and the brand selling the film entirely, which is kind of risky -- just a bit -- when you consider the director has no track record either. I'm surprised there isn't one dependable actor -- or at least a "known commodity" -- in the film, to be honest.