Unlocking every dinosaur in Jurassic World Evolution 2 requires the player to do a little bit of hard work.
Jurassic World Evolution 2: How to Unlock All Dinosaurs
Unfortunately for players, you can't do expeditions or research in Sandbox Mode, which is the only way to unlock dinosaurs and buildings in the game.
As the game is designed, you have to play outside of Sandbox to unlock anything fun for the do-anything-you-want mode, whether that's through the Campaign Mode, Chaos Theory, or Challenge Mode.
Essentially, those who play the game are required to grind like crazy to unlock every dinosaur in Jurassic World Evolution 2.
As you play through one of the other three modes, all of the dinosaurs and buildings you unlock will automatically be available in the game's Sandbox Mode.
For example, to unlock everything for Sandbox Mode, the player has to finish all three other modes in the game. This is shown through the Campaign mission that is the only way to unlock the Allosaurus.
The developers encourage players to play through the other modes of the game besides Campaign as well, as shown by the tweet above.
Players can check out the game for PC and console here.