[semi-extrinsic]

I came to say the same as GP. In my world, if you don't solve time-dependent coupled PDEs in 3D you're not doing real physics. In someone else's world, if you don't have particle-in-cell functionality or symplectic integrators or P3M methods or whatever, you're not doing real physics.

To my mind any software that calls itself a generic physics engine is not doing "real" physics, more like "Blender physics".

Of course this can still be super useful! But the field of numerical physics is super broad and deep, and different sub-fields require dramatically different data structures and algorithms.