Every list of beach destinations is the same handful of resorts. These are places where the beach is one good reason among several, so the people in your group who don't want to lie on sand for a week still have a trip.
A beach, a mountain and Gaudí, all reachable on foot from a single apartment.
Three or four completely different trips sharing one island.
A Roman palace you can live inside, and a ferry terminal to a dozen islands.