With the beginning of the war I meant the time Japan entered the war. While Zero was a 1940 design, it hadnt been upgraded, at all, in the nearly 2 years, while for example Bf 109 and Spitfire had went through many updates. That did include ability to carry droptanks to nearly double their range. (AFAIK first drop tank equipped E-7s did make it to Battle of Britain, but too few, too late, and IMHO the lack of (non Bf 110) fighter range was only one of the reasons to Luftwaffe's loss.)
But that is again lack of will and resources to change an already flawed existing design, while at the same time being equally unable to design new models in acceptable time due to the same reasons. No nation "got it right" at the first try but the inflexibility of Japan's military burdened them even more than many others, and combined to the more limited resources they had compared to US, UK or Germany, they quickly fell behind. Even before the war had begun.