Admiral John Byng wrote:
Well, your last paragraph says it all. Japan was idiotic to start a war they could never win.
But that is a completely different topic

This is true for all Axis powers, they were gamblers and thought that it would be worth to risk everything. The result is well known: they lost nearly everything and were responsible for millions of deaths and the devastation of their countries.
Admiral John Byng wrote:
My point is that if they had understood carrier power better than anyone else they would have ditched the useless Yamato class battleships and built big carriers (not Junyo, Ryujo etc. which were little more than escort carriers) and sorted out their ridiculous training regime and that may have given them another year to wait for defeat.
But did anyone argue that they understood carrier power better? Or did you argue that all others understood carrier power better than the IJN? For the first question you are right: they do not concentrate fully on carrier power, but stick to built battleships for the final, decisive battle, which never happens the way the IJN expected it to be (as in Tsushima). Therefore the battleships were there at Midway: for the decisive battle against the USN. They were deployed at every situation the IJN command expected such a battle to be possible. But they also stopped to built battleships before the RN and USN, even converted some of the battleships to carriers (Shinano, Ise class).
For the second version you are wrong: there is no indication that the RN and USN understand carrier power better, at least not before the war or early in the war.
For the Great Britain it should be sufficient to point at the available carrier planes early in the war (completely inadequate, especially if compared to the IJN and USN ones or the land-based aircraft of the Axis powers!), for the United States the continues effort to built battleships (even after Pearl Harbour!) tells everything. E.g. as AAW ships to protect carriers more ships of the Atlanta/Oakland class would have been much better - and much cheaper, therefore much more of them could have been built instead of the Iowa class. Somehow the USN still thought that they needed battleships to protect the carriers against surface attacks. For sure they were useful as fast AAW batteries, but were a very expensive solution to that problem (with useless 16 in guns).
/edit: DavidP: is this really true? It is often mentioned, but the IJN used carriers for attacks already in the First World War (against the German base Tsingtao) and also in the 1930s against China. The carriers planes were the logical successors of the torpedo boats used e.g. for the initial attack on Port Arthur in the Russian-Japanese War, used as equalizer against a stronger battleship force.