You're confusing personal preference with objective quality. Your palate is shaped by what you've grown up eating, so naturally, if you're accustomed to American-style pizza, traditional pizza might not be what you imagine pizza should be.

That doesn't mean Italians are bad at making pizza. It means you've developed a preference for a particular interpretation of it. Someone raised in Naples might have exactly the opposite reaction to American pizza, in fact I imagine that's very likely give the fat saturated nonsense I've experienced there. Deep dish pizzas are a crime, who the fuck wants more bread in their pizza.

The fact that you've managed to visit the birthplace of pizza, discover that it doesn't cater to your particular tastes, and conclude that an entire country doesn't know how to make its own food is quite something.