Keep in mind that few if any people post on a maintenance forum unless they have a problem. Those that are simply driving and enjoying the ride don't have a reason to look for help. The view then is distorted.

The W123 with the OM617 engine is one of the auto industries success stories. They are solid and reliable. Mine has 353k miles and I would get in it tomorrow and drive anywhere. We also have a W211 Diesel but my w123 is still my preferred ride on long distance trips. Part of it may be the attention it gets but I still prefer the feeling of solid mechanical reliability.