How pivotal was the Battle of Midway to the allied victory in WWII?

To second Park.

Midway was a large momentum shift, but it was not the moment Japan lost the war as many like to portray it. Both when we consider the underlying economic imbalance or how Japanese high command, those that knew, at least saw it. It was a set back to be sure, but along with his fatalism, Yamamoto had a mean streak of arrogance and his lofty expectations for the attempts to retake Guadalcanal show he thought nothing was settled. While the lingering fight and his own death did much to dampen the mood of the Admirals come 1943.

It took Japan essentially from a position of strength to one of parity with the USN. While the sizeable number of air crew, and ships company saved from each carrier provided the strong Cadre to maintain strong ground based Naval aviation and her remaining carriers. Including her 2 most capable in Shokaku and Zuikaku. While the first if the Essex class ships were about a year away. Enough time in Japan's mind to isolate Australia, secure her holdings, and hopefully bleed America to the table

As evidenced by the bloody carrier clashes of the Eastern Solomons and Santa Cruz the Kido Butai still had the ability to defeat or at least savage the USN. Even if the cost could be staggering. While the surface actions off Guadalcanal demonstrated that while the USN could rely on radar more as it matured, it was still not perfect, while IJN light forces were dangerously skilled at night actions.

While the blows in May and June of 1942 created the breathing space and near parity the USN needed, Watchtower and the invasion of the Solomons was a near run thing.

Thus I do agree that where Japan's situation went irretrievably to the red is better situated in the lower Solomons in October and November of 1942.