This also is not true, the CPC was an active force in the war against the Japanese. Especially in the North China Plain the guerrilla forces were able to create a sea of resistance around major urban centers, rescued downed US aircrews and escaping Allied POWs, tied down significant IJA forces, and perhaps most critically, they totally undermined any attempt to garner popular legitimacy from the new Wang Jingwei regime in Nanjing.
Remember when the red army hid in holes in fucking mountains to avoid fighting the Japanese?