Aren't Unity still using PhysX? A lot of engines are still using PhysX (albeit stuck on version 3.x). Upgrading a physics engine is often a pain point, either

Aren't Unity still using PhysX? A lot of engines are still using PhysX (albeit stuck on version 3.x). Upgrading a physics engine is often a pain point, either because it is so tightly integrated in the code base or because game assets have been tuned for the current physics implementation and even a small accuracy or behavior change will require assets to be re-tuned.