China respects Japanese military prowess notwithstanding Japan's pacifist constitution. And the Chinese Communist Party has worries that their shiny military isn't as good as the shine makes it look.
The Chinese military was publicly criticized by CCP leaders for not training effectively and tolerating low levels of readiness. This is an ancient Chinese tradition along with corruption in the military. For centuries Chinese government have been trying to eliminate these problems but have not made a lot of progress. To help with these anticorruption efforts, the CCP has imposed a system of parallel political officers working with unit commanders as low as company (a hundred or so troops) level. These replace chaplains that are so common in non-communist forces. The political officers are there to assure loyalty (to the CCP) and monitor effectiveness. These effectiveness reports are considered top secret and extremely valuable because they provide the most accurate measure of how loyal and effective the military is. While state-controlled mass media boasts of all the new weapons, equipment and capabilities Chinese troops have, the political officer reports are much less encouraging. [emphasis added]
One can hope that this Chinese weakness in quality is ingrained culturally and too difficult to overcome. But I wouldn't count on it. Even a twenty year period of a particularly energetic leadership that overcomes the problem temporarily could cause a lot of damage. Especially when nukes are involved. But even without them.
I think our Navy is better run and crewed than the Chinese navy. But a combination of Chinese numbers, modern weapons, good enough crews, and the initiative in starting a war against our outnumbered forward units could put us in a difficult position that risks our defeat.
The Chinese navy is rising. Can our quality and firepower plus our allies overcome that? Probably. Given enough time.
But are we really sure our qualitative advantage is big enough to overcome Chinese numbers?
And what if the Chinese Communist Party convinces itself that despite its own quality problems that America is really no better? We can't define how the CCP defines rational.