They aren't of the 'elemental' type because the printed books do not have that printed in their stats. And that appears to be the most important thing to most players-- what is printed in black and white in the books. Even if they could change it to something else they'd prefer or add a new type or whatever... that "doesn't count". If WotC prints it, then it's true.
Goblins are 'fey' now and apparently we have to just deal and accept this travesty. Even though we could (and do) just easily ignore that tag... nope, by a lot of people's standards that just the way it is and it sucks and WotC sucks and they're stupid for doing it, but we don't have any choice. Goblins are fey creatures cause that's what the book says. Which means by the same token... ethereal creatures have no creature type and we just have to accept that reality.