Why hire a big star like Scarlett Johansson?
The Jurassic Park franchise never hires a star. When Jeff Goldblum, Chris Prat, and Bryce Dallas Howard did the movies they weren't stars, for Christ's sake some of them weren't even in B-tier, but in C-tier.
Everyone knows the real stars in the franchise are dinosaurs and VFX. To hire a star like Johansson, the movie needs to spend at least 20 million on her salary, not to mention the back end.