Inheritance based OOP models tree-like entites well, where hirachy is defined and clear cut. Unfortunately, lots of real life domains are best expressed by graphs - commonly a DAG. You need to pay attention to your edges and not just the nodes. Inheritance based OOP gives you one keyword to express your edges: extend, and it's horribly inadequate. Mutatable state is not a issue in Java OOP, lacking the expressive power is.
Trees can be modelled with sum types, the mathematical dual of product types (records). Java doesn't have sum types and so inheritance has to be used to encode them.
