I´m sorry, but I disagree. I´m not saying (and doubt anyone does) that the current MBs are the worst looking in the company´s history. That would be laying. In fact, I´d say every current MB looks good. BUT, if you review the company´s history, you´ll find that 50 years ago, MB was superior in both design and tech. People bought MBs cause they were simply the best cars on the market, and looked like that. Afterwards the competitors started to improve in terms of looks, but MB still had the edge in the tech department, being the most advanced cars with the best engines.
It´s true the models you say looked like crap, but still had an advantadge over BMW and Audi, and people believed buying an MB they were buying a car that would last them forever. Nowadays, an MB is not better looking per se than any other german car, it deppends on the customer likes. And not only that, they no longer featured the best engines. Not every MB engine is better than the competitors offering.
Thus here we are. Currently, people see the Mercedes cars as something for old wealthy guys, as they think other brands have better looking cars, and they don´t think the star is a guarantee of a better tech/engine.
The bottom line is that Mercedes Benz is no longer as special as it was. And I doubt the current cars still look nice in 20 years.