You are correct. Not until it was too late to make any difference (Leyte Gulf, Okinawa) did the Imperial Japanese Navy throw in its capital ships - by which time the air and Naval superiority of the USN was overwhelming and the Japanese ships became target practice for it ... but you are right - the same spirit at Guadalcanal could have won that battle - and prolonged the war in the Pacific by a year, in all likelihood ... with the same inevitable outcome ... but even more lives lost on both sides ...
The Japanese did not have enough tankers to operate as a unified fleet. Their carriers were based in the Home Islands, while much of their battle fleet road at anchor in the Dutch East Indies (where the fuel was). US submarines prevented all that oil from circulating freely withing the Japanese held Pacific areas.
After the loss of the Solomons the Japanese were planning for a major battle in their inner defensive ring where they could bring both wings of their fleet into play along with most of their airpower. In other words, “It was by design”. The IJN was husbanding their strength for a single battle that they hoped would prevent their eventual defeat.