As per the patch notes, it appears that Island Sanctuary is accessed through an NPC in Lower La Noscea. I do not believe that it is in the best interest of the player for this to be the sole means of access to the island, and I do not understand the reasoning behind this decision given that teleportation can be used to reach nearly everywhere else including the Housing Districts.
In the future, I would like to see the ability to teleport directly to the island be added. I feel that it is important to make clear the desire for this feature early on, so that the content is easier to access and help people be more willing to partake in it.