Where has usability gone in car design?

People appreciate all the luxury coming with nowadays' cars. But are they really more usable? I just drove from Berlin to Switzerland, with a Mercedes 300 SL, a car designed at the end of the 60ies, built for 18 years until 1989 and a modern classic car today. It's also an impressive car from a usability point of view.
It starts with the fact that you can see everything, even with the hardtop mounted. You even can see the cover of the trunk when you are going backward. No need for cameras or "park distance control" systems.
The manual is short, really short. All what you need to know to operate the car is covered on less than 60 pages. Have you looked at the manual of the son's son of the 300 SL - the 350 SL built today? You need to read through hundred of pages before you are able to properly adjust the air condition. Actually you can enter and drive the 300 SL from the 80ies without even reading the manual at all, everything is where you would expect it. And there's not that much to fiddle around with anyway. There's no airscarf, no air condition, no ESP, no park distance control, no navigation system, no distance radar, no .... It's basically a car with four wheels. But everything you need for your daily motoring is there, even mirrors that' can be adjusted sitting in the car, the right one electrically the left one mechanically. Good so. The heating can be operated with basically two wheels, you won't need a manual to understand the concept.
And while there may be good reasons that the windows in modern cars are so small, mainly because of passive safety considerations, I prefer the "active" safety of being able to see everything out of the old car, be it children, other cars or a bicycle.
Maybe the designers of modern cars should have a ride in one of these older classics from time to time to have a benchmark on usability.