The simple answer is that the materials, workmanship and engineering of these old microscopes will never be repeated again.
The optics are the easiest thing to copy. It's not enough to cut and polish the glass. Their coatings, seals or optical cement, are all required for longevity. This is just one area of supremacy in which these microscopes excel. Much has been said about LED longevity, as if that's all there is. For example, I have a new Stanley LED flashlight at home which after only an hour or so stopped working due to a cheap switch. I've seen cheap NiCad batteries which only take a couple charge before failing. Even the rheostats fail because ALL the parts are made as cheaply as possible.
What people don't realize is that the matterials and workmanship required to move an object both vertically (fine and coarse adjustment) and horizontally (stage X,Y) at 1000x magnification without play or chatter is no simple matter. To accomplish this in such a way that it still functions a half a century later is exponentially harder.
Timeless classic microscopes are built to last generations and can be renewed and returned to service if you have the skill and knowledge. Even breaking down a mechanical stage can be a Rubik's cube like experience. Coatings on the old German microscopes are rock hard, probably because they invented them. I clearly remember even Olympus eyepieces with scratched tissue thin coatings even back in the 1970's. Like I said, the matterials and craftsmanship are gone, and the disposable, unreliable and unsupported microscopes from China have arrived in their place. That's why I have been collecting and waiting. Now is the time...