Gaza was never a state. There was never an institution in Gaza that controlled Gaza’s borders, its airspace, or its sea access. There was never an institution that could issue passports with which Gazans could travel abroad without interference. There was never an institution that could collect customs revenue. There was never an institution that controlled water, electricity, medicine, or food imports.
Most critically for any useful definition of the state, there was never an institution that exercised a monopoly over the legitimate use of violence, because the Israeli state could and did export violence and kill Gazans with impunity.