The problem of shortage of pilots was not unique to the Axis. The Americans and Soviets also had that problem. The only ones out of the major powers who managed to mostly avoid it was the British and that was due to the pre war Empire training programs in Canada, South Africa, India and AusNZ.Two of the main problems with the IJN were the same as the Luftwaffe: their training programs and their mania for not rotating pilots in and out of active duty. German and japanese veterans flew untill they died, regardless of time in duty; meanwhile, training was carried out by instrutors that(for the most) had little combat experience. Alied pilots were rotated back, and many went on to training units, to pass on what they had learned. This meant that new alied pilots had far better tactical training in middle/late war than Axis pilots.
Generals on **all** sides, as amazing as it seems to us today, severely underestimated how much material their industry could produce and how fast.
To take one example, the Lancaster was in full scale production for 2 years. In that time over 7000 examples were completed, about 70 a week/10 a day. Once the prototype was ordered into production, and the machine tools setup, they would churn them out.