I don't think the computational complexity has been a significant problem for at least half a century. Aspheric lenses are described by simple polynomials and r

I don't think the computational complexity has been a significant problem for at least half a century. Aspheric lenses are described by simple polynomials and ray tracing is just elementary geometry. You only need to analyze a hand full of rays to get the relevant parameters of an imaging system. Probably a few thousand floating point operations in total. The problem is that it is extremely difficult to manufacture surfaces with optical quality that are not spherical. Even today, aspheres tend to be more expensive than spherical lenses and have significantly worse surface quality. This is the price you have to pay if the objective has to fit inside a phone.