Oh, I totally agree. It was backwater in the sense that it was not a priority for logistics and supply, but it was critical to the war effort and one of the most difficult theaters for the troops who fought there. Jungle warfare, many times in mountainous regions was brutal stuff -- like the Kokoda Track battles in New Guineau where the Aussies held the Japanese off from Port Moresby.
I read a book once, now lost, called Jungle Dive Bombers, which talked about how planes like the Vengenance and the Vindicator and the Skua and others that didn't have much value in the front lines in the Pacific and Europe were invaluable in the jungle, where larger bombers couldn't pinpoint and hit the smaller targets presented by jungle warfare.
And, a little known aspect of the war is how badly the Burma campaign went for the Allies for so long. The Japanese push into India in 43 and 44 was very dangerous, and the "rebel" Indians raised their own army to assist!
Amazing history in the East, starting with the AVG in China and the battles in Malaysia and Java, and then Singapore and the loss of Force Z in 41, and then Burma and India later in the war.