User of 3D CAD here. The reason this is so hard is that a part's geometry will be governed by a different set of parameters, depending on its function, and the software will not know the function of the part, unless is was written by a domain-specific expert.

I'll give the simple example of a hex-headed nut: how will the software know that the flat-to-flat measurement is critical (since it corresponds to the wrench/spanner needed to drive it) rather than the point-to-point measurement? In less trivial examples, questions like this need to be though out when creating models, and require domain-specific knowledge that a ML model will not have.