"This supplement contains a wide variety of elementals that are ideal for both DM's and players. "
This is just statblocks and monsters. Not exactly breaking ground. Heck, they give stats for Cryonax and others, telling me that this is just someone who wanted 5e stats for things that WoTC didn't make yet. Sure, they mention that they made a salt mephit. A salt mephit doesn't mean anything at all about the plane of salt, it is just a monster. Heck, I've never sent players to the plane of fire, but I sure have used fire elementals. One does not need the other.
Elemental Compendium I: Creatures of the Inner Planes - Dungeon Masters Guild | Dungeon Masters Guild
Cool, player races. Still not giving me any reason to visit the Plane of Salt. Not a single thing is going on in the Plane of Salt, even if you have Genasi of Salt running around the world on adventures.
Greater Genasi - Dungeon Masters Guild | Dungeon Masters Guild
Adventures? Things actually happening in the PLane of Salt, let alone the intersection of the plane of salt and the plane of ice? Or just "salt monsters" which I don't need an elemental plane of salt or an elemental plane of salt and ice to create, use or explain?
Just the monsters? Then I stand by my previous statement and how your "just use the search function" was a rather useless counter-argument.