[uneniaPhenits]

But why does a "non-believer" not believe? It's because they can't see any reason why Islam is any truer than another religion. It doesn't make sense that a good person would be punished.

If a good person with good charecter says to his father 'you are not my father', will he continue to be a good person after denying his father? No.

So Imagine denying one own Creator Allah the Almighty. All these laws of Islam is set by Allah , sometimes it may not be clear to us, but remember Allah knows everything and indeed only He knows whats best for us.