There are some tasks on the island that the Resident Representative (first resident on the island) must complete before the related features will be open to other players. For example, only the Resident Representative can receive and set up Blathers’ museum tent. Once the tent is in place, all island residents can donate items to the museum.
It is not possible to reassign the Resident Representative role to another player. If certain places or items in the game aren’t available for island residents, have the Resident Representative progress to the point where the item or feature is available for them, then try again.