"Polymorphism is nice as well, although I can't grok (yet) why this is necessarily not part of non-OO things. I'm not clear that it goes with the strong binding of state and method in a class."

Polymorphism isn't necessarily part of OO. Python actually has polymorphic functions outside of class …

There is a Design Pattern, sometimes called "Don't Talk to Strangers" that embodies the OO design principle of "Responsibility Assignment". This pattern can also be called "The Opacity Principle."

Sometimes I like to describe it as "If you don't control it, it's none of your business what's under the hood …