Indeed, one of the pillars of OOP is encapsulation. (= encapsulation of state = hiding state = every object can maybe be stateful, but you can't know from the outside).

Meanwhile, one of the pillars of modern programming techniques (FP, React, and others) is to make state very explicit and separated from the rest (Think State Monad, react's useState, etc), because statefulness is now correctly identified as being a major source of problems.

So OOP took us completely in the wrong direction regarding state management, for 2 decades... Understanding in 2014 that was liberating for me.