> The ICC is overwhelmingly popular with most countries and people, most people who oppose it are those from countries which harbor war criminals

We don’t have good enough contemporary global polling to confidently say that a majority personally supports the ICC.

However, I suspect you’re right that most people probably support the idea of the ICC but countries choose not to be part for a variety of reasons, other that “harboring war criminals”.

The following countries are not party to the Rome Statute, which is what established the ICC:

United States, China, Russia, India, Israel, Indonesia, Pakistan, Turkey, Saudi Arabia, etc.