The thing about the Russo-Ukrainian war is that it is a failure for both sides. The primary lesson from this war is, how do we avoid ending up like those poor guys? If the US Army fights a war with anyone, let alone China, on the doctrine that it should set up a static attritional front line with drone warfare, the joint chiefs should all be fired.
Don't have Germany be so dependent on Russian gas. Don't tear down nuclear power plants, build more of them instead.
if the US ever trains with ukraine like the brits did, youll find that the current doctrine has no ability to move against ukrainian defensive lines.
this is the current state of the art. it will be a major innovation if somebody figures out something better than "travel during fog"