No need for insurance.
DCL is allowing cancellation within 14 days of embarkation if exposed to or positive for covid. Full refund, no penalty.
As for testing positive at embarkation -- DCL will refund or credit towards a future cruise. They offer transportation back to Orlando wherever you want -- MCO or hotel or other. But it is on you to make those alternative plans; DCL does not put you up in a designated hotel or provide transport home.