Do you have to? Isn't it enough to know that some people do, and that the system should not needlessly mock them?
I agree Elemental Adept is not worth it for a Wizard. A Dragon Sorcerer, on the other hand ...
Please explain how it is worthwhile for a dragon sorcerer.
Also there is plenty of inspirational fiction from the Don Callander books to the Avatar tv series where element weilders are absolutely limited to a single element, why mock someone who wants to stay true to the source fiction?
I have no problem with theme PCs.
It's just as easy to use cold spells against the fire creatures, and fire spells against the cold creatures, and your chances of hitting into the wheelhouse of their vulnerability is even greater.
Without spending a feat.
I never understood the concept of gimping your PC for a thematic reason.
So by your definition, if people think that the feat pretty much sucks, even for theme PCs, then those people must be mocking those players.
I just think that gimping your PC with a lousy feat is dumb, for any PC.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.