I have a friend with a brand new Lexus LS430. It rides very nicely but you get a lot of the bumps and sounds that the 126 suspension gets rid of. I think the design of the 126 suspension is to be more communicative than more common marshmellow luxo boat. Its not ultra smooth like a caddy or a lexus but it does move over the road well and is quite comfortable.

If you look at the time period that the 126 was built for it was probably quite good for its time. Luxury cars have evolved over time and people expect different things from their cars. I like to think of it as the "lexus effect". BMW and Mercedes cars were cupholder devoid teutonic autobahn cruisers before the American motoring public wanted a softer ride and the common luxury features. Technology has evolved as well to make cars lighter and quieter. If you drive vintage cars regularly the whine of a rear differential or road noise or suspension stiffness does not bother you really.

Additionally as the fleet of 126's ages the rubber that isolates our suspensions ages differently depending on the part of the country that your in. Unless your driving on a freshly overhauled suspension with new bushings its difficult to compare the 126 to other cars. Even a 1991 model now is a 15 year old car. My 1982 model is over 24 years old. I have done several upgrades in my car such as engine mounts and other small old rubber with amazing results. I grew to accept my diesel engine being a bit on the "rough" side at idle until I replaced my engine mounts. After the replacement the only difference between my car and a gas car smoothness wise is the distinctive clatter under the hood.