Japan could replace oxygen torpedoes without changing the Pacific War alone

How would the Pacific War change if Japan rejected oxygen-enriched torpedoes as too dangerous?

Probably not by much on that change alone; Japan could build another large torpedo, and the result would depend on its performance.

Abandoning oxygen enrichment would remove the historical Type 93 approach, but it would not leave Japan without large and powerful torpedoes. The effect depends on the replacement weapon rather than on oxidizer choice by itself. A conventional design could retain much of the threat while changing range, warhead, or handling tradeoffs. The Pacific War would probably follow a broadly similar course unless the substitute torpedo performed much worse.