One alternate rule that I’ve used that slows the game down well and makes terrain in general more useful is that you only begin with home islands, and you can use a ship’s action for the turn to “discover” an island, by placing an island at least L-away from that ship, and 3-L away from any other island. Then the player to your left places a piece of terrain within S of the island, so typically between the ship and the island.
I feel like that could get pretty gamey but I have wondered multiple times about how to make the game more realistic in terms of exploration. I’m not sure how to best go about it though since it’s difficult to restrict sight and not see the entire setup.