Salem, the town proper that is, not the spooky museum, seems like yet another missed opportunity for a perfect settlement. It even already has its own quest, some defenses, and at least one settler with the hope of more. Yet after you help crazy old Barney nothing happens. You don't get to build in Salem, Barney continues to bizarrely have his own one-man militia and act like the Minutemen never existed, and nobody new comes to the town even though it's totally safe.
While you could argue there are already other nearby settlements... Coastal Cottage isn't really that much of a settlement. It really looks, and feels, like somebody just half-assed a workshop into the barn and called it a day.