> Maybe old fridge are less efficient than new ones, but for what reason ? electric conversion ? bad radiator ? stupid motor ??

Motors are simple. My blind guess is that it's a mixture of improved insulation and improved heat flow.

Though speaking of heat flow, stand-alone fridges always come with requirements that they need a certain amount of space for the heat to escape the rear of the fridge. Builtin fridges don't have that heat. I now find myself wondering whether builtin fridges can ever be as efficient as standalone ones.

And you're right that it can be advantageous in the short term for quality companies to cut costs by cutting corners while coasting on their reputation. Who knows, AEG might be doing that right now. Your AEG beard trimmer makes me regret we didn't go with Bosch or Miele after all.