[Little Ray]

The pre-war IJN also had ridiculously difficult (and brutal!) training and high standards for aviators. This cut the pool of available aviators and made it difficult to replace losses.
Once the war turned against them, the standards were lowered, but the damage was done by then.

[CougarGA7]

Once the war turned against them, the standards were lowered

I guess you can lower the bar when you only expect them to fly the plane once. :)