That power differential was exactly why Imperial Japan built the Yamato class. They knew that the other powers were building to treaty limits and thought that they could gain a qualitative advantage over them by building such massive battleships.
Right, but again- that's a question of state objectives. What are super heavy battleships for? Engaging other capital ships from world-class fleets.
The thing is, Japan
couldn't beat those fleets. It could have built the very best battleships- it did!- it could have built the very best carriers. The USA had more. Even a Royal Navy unchallenged by the Kriegmarine and Regio Marina might have been more than it could chew.
And even if it had beaten them- what for? Now it has an empire in the Pacific that it can't hold down without getting out of China, but if it's out of China it doesn't need the empire in the Pacific.
The war in China itself was probably unwinnable- at least by the standards set by the militarists- but if you're going to spend seventy thousand tons of steel in the service of empire, then spend it in Manchuria.
Or, ideally, spend it on civilian factories and don't get involved at all.
But ignore the old problem of how Japanese doctrine, strategy, political objectives and procurement never matched up- there's really no navy that needs the super-Battleships. Yes, they do their job very well. But, again, what nation needs them to do that job that well and can't accomplish it with smarter spending plans?
Germany certainly doesn't. Italy doesn't, even if it had the capacity to build the damn things. Britain doesn't. The USA doesn't.
You don't need hindsight to realise that putting that much of your industrial output, that many men into a single ship is not a good idea. It's a big ship- but it's a much bigger ocean...