is there at all such a thing as mezonot "bread"?

No, there is no such thing as "mezonot bread" in the way most people try to use it. This is a made-up excuse that people use to avoid saying Birkat HaMazon. Let me be very clear about this. In order for a bread to be mezonot, it would have to be made from much, much more expensive ingredients than what any pizzeria or bakery is willing to use. The bread would need to be made with an extraordinary amount of milk or fruit juice - not just a little bit. It has to be baked differently. It would cost you ten times the price - we're talking about fifty dollars or more for a pie if it's pizza. No one does this. I don't believe there is more than one place in probably all of America, if there is a place at all, that has real mezonot pizza or bread. Anyone that is a real talmid chacham, anyone that really has any level of yirat shamayim, even for a tiny little bite of pizza, they do hamotzi. There's no such thing as mezonot. The reality is that pizza is almost impossible to be mezonot if it's sold for anything less than fifty dollars a pie. People look for this excuse because they don't want to say Birkat HaMazon. They'll eat pizza the size of their head and ask "Is this mezonot?" It's not mezonot - it's hamotzi. And by the way, it's not just about the makeup of the bread - it's also about how much you're eating. If you're eating two slices, it's not mezonot. If you're eating even one regular slice as an adult, you should do hamotzi and Birkat HaMazon. You know what's amazing to me? That HaKadosh Baruch Hu doesn't impoverish people who try so hard to avoid thanking Him. They have time to eat for three hours, but no time to say Birkat HaMazon. This is pure ignorance. If people actually knew what the Torah says about Birkat HaMazon - that it's the number one blessing in all of Judaism, more important than Kriyat Shema, more important than Amidah, because it's the only blessing that's written directly in the Torah - they would be running to eat bread just to say it.