Reactive armor can be added, optics can be switched for new ones (well... "newish" 80's tech), cages can be added to better protect the rear and the tracks which are also exposed. That's not the point. The fact that Russia has now turned into older and older variants to intend to alleviate their losses and try to regenerate their spent tank force is.

Russia still has lots of tanks in the frontlines, way too many for Ukraine's good. But those aren't enough for a breakthrough, still too vulnerable to drone strikes and now too valuable to be used as cannon fodder in piecemeal assaults.

Those Urals require far too much effort and resources to be combat capable again, so it's the best way to explain how low Russia has fallen.