Is it fair to reduce OOP to mere hierarchical composition of data structures?

Question

Meaning that OOP allows me to have data-trees, of arbitrary depth and breadth, with some leafs being functions (and those leafs would be called methods) ?

Because everything else that people often put near "OOP" mark, just don't seem to have anything to do with it. (Inheritance, subtype polymorphism and encapsulation seem to be orthogonal to OOP).

Am I right? Or I'm missing something ?