This problem is partly a type system limitation however.
In a more flexible type system with union types and other magical features, your example problem would be less of an issue.
However Java has an extremely limited type system so there is no middle ground between composition and inheritance. Once you choose one way, there is no “middle step” to migrate over.
Union types are very rare (scala, typescript are the notable ones I can think of that implement it), most other languages only have sum types (which includes java as well, see sealed interface/classes), where you have to create each unique set of types you want to use separately, wrapping each option into a marker type basically.
In a more flexible type system with union types and other magical features, your example problem would be less of an issue.
However Java has an extremely limited type system so there is no middle ground between composition and inheritance. Once you choose one way, there is no “middle step” to migrate over.