The problem is that Japan is not constrained in any significant way early in the game. He has essentially unlimited fuel, supply, and transport shipping. Disruption of Command and control is not a factor. So disrupting him doesn't do much. He just reroutes a couple fleets the next day, tranfers in a few more air units and Viola everything is under control.
Fleets can stay at sea forever, air units can rebase from 500 miles away to a just captured airbase and fly missions that day. Fuel Fuel and supply everywhere. Where are the constraints on Japan?
A few thoughts.
1. I'll agree that Japan is essentially unconstrained regarding supply - in total this is not true [try doubling the capacity of all your factories in the first six months - like I did in my first game !!!] - but an experienced player will have it where needed, when needed and will work to avoid overall shortages. So, first point is agreed.
2. However, regarding time and space - the "three beasts" ... i) KB ... ii) The 6+ BB Surface Group ... iii) The Betty/Zero LBA group ... cannot all be everywhere all the time. We see some people advocating for an attack on India and others advocating to capture the entire CENPAC/SOPAC region. To do these things quickly and without much risk would involve use of KB. We see many players advocating for keeping KB together and not splitting it up. All this implies some constraint. KB cannot jump from the Bay of Bengal to the Coral Sea in one day. Even staging the Betty/Zero LBA force from the Bay of Bengal to the Coral Sea takes several turns - to include some rest.
3. Force - the Japanese have a lot of force, but even from the start of the game if you were to line up the Japanese force side by side with the Allied force, the advantage is not so huge. The key difference is interior lines, essentially the Japanese occupy the center of the map, the Allies the edges. But given some constraint due to time and space, it should be possible for the Allies to concentrate suffficient force in some areas to achieve at least temporary local superiority. Also in the force category is LCU. The Japanese certainly do not have unlimited LCU available for operations outside China for at best some time. We've seen some "amazing" things done with these few units in recent months - but the ability to do everything, everywhere all at the same time, still doesn't exist.
4. Human - perhaps the most important constraint is the Allies are playing against a human player [ assumption of this thread ] - who while certainly better than most non-human players - has certain weaknesses. Players will drift into patterns - if these can be detected and predicted - advantage can be gained. Defeating the ( mind of ) the enemy player should be the true goal for either player. We read AARs often where one side guesses what the other will do - and then we see demorilization on the part of the foiled player. Also human players may react emotionally and feel that they must hold on to a lost base/plan/operation for the sake of "honor". A truely perfect "AI" of course would not make this mistake. But the love of patterns and the emotional nature of most players offer another constraint on the Japanese.
5. Summary. By its very nature, the Japanese expansion into the map edges increases the effects of the contraints on time, space and force and ultimately the initiative is lost, there is simply too much territory to defend and not enough force to defend it - or to be able to switch enough force back and forth across the map across the now greater distances to counter the growing Allied force. This can cause the Japanese player to "take a moral check" which is one reason I think we have seen many games end in early to late summer 1942. The Japanese player "fails" his moral check. But assuming this does not happen. Can the Allies delay in some areas or return in others and avoid suffficient huge relative VP loss and cause some attrition on the Japanese and do enough to stave off the 4 to 1 VP ratio by 1 Jan 43 ?
I won't say there is no magic Japanese victory plan - there might be one - but as you say WITP is a lot more complex than the few games which are known to have been "solved". For exampe Checkers, which has 24 "units" operating on 32 "squares" ( not sure how many units and hexes we have in WITP but it is more !!! ) has still not been "solved" to my knowledge - although I think a group is closing in on that result. To "solve" WITP will either take a true genius or a lot of luck, assuming that it is possible. And given the complexity of "solving" games like Checkers and Chess ... I'd still bet against any of us "solving" WITP anytime soon. But ( as a trained mathematician ) I can't completely rule it out, I do not know that it is impossible ( to solve it ).