As legacy fenics only supported simplices (some limited support for quadrilaterals and higher order non affine geometries) all these operations were well defined.
Many of these functions are no longer trivial to obtain
Midpoints can be Gotten with
https://docs.fenicsproject.org/dolfinx/v0.7.0.post0/python/generated/dolfinx.mesh.html?highlight=compute_midpoints#dolfinx.mesh.compute_midpoints
For cellarea/volume see: Computing mesh element size - #2 by dokken