What car manufacturer in business today has the engineering & build quality of the W123?

Ans: Toyota.

It isn't the Toyota mechanicals, IMO, it's their electronics. Toyota can draw on the best electrical engineers on the planet. Europeans and Americans draw on a less proven cohort -- I doubt I need to list the examples. In my lifetime I have seen people change from a hearty laugh at the silly Japanese "transistor" radios to, in less than a decade, the Japanese owned the electronics market (aside from a few extremely high-end non-Japanese mfrs). For the following 30 years the Japanese have led the innovation (if not the invention) of electronics.

We consumers demand items in our cars that are electronic-dependent or more easily solvable with electronics. The Japanese are working to their strength and kicking everybody's ass doing it. Good for them and good for consumers. Too damned bad for western automotive mfrs.

B