Have JMSDF Kongo/Atago-class ships visited other countries, though? I don't think many countries would trust China with visits from its highest-tech ships. Aren't there any countries China trusts?
It is NOT only a matter of trust. Most nations don't have hi-tech navies. Most nations use their navies for local purposes, not worldwide functions. Most nations do not send their naval ships around the world on a regular schedule. Hi-tech navies are mostly found in America, Europe, Russia, South Korea, China, and Japan. China's modern navy is very young and so are China's worldwide economic and political relations.
Even then, what are the pros and cons of China sending naval ships to visit other nations compared to China developing direct political and economic tires with other nations? That is a question for China's and other nations' leaders.
Then there are international politics mixing with the military. Singapore was recently allowed by France to send its advanced, French-made destroyer to visit China, but Singapore is NOT allowed by America to send its American-made jets to China. If you ask me, South Korea is more concerned with Japan than China, but America insists that South Korea acts nice to Japan and defends itself against China.
Then there are different degrees of trust. America sends its military to many nations and conducts military training with many nations, but America has different levels of trust with each nation it trains with and vice versa.
Many times, international visits and training are more about mitigating problems than cultivating trust. When America visits and trains with Russia (which is rare), it is for easing the political tensions between the two nations and creating agreements to avoid destructive misunderstandings, and not about building a military friendship or alliance.
I can go on and on, but the moderators will probably warm me for going off-topic, so I'll stop here.