I agree that the Wilden and Shardmind are a bit conceptually lacking and unnecessary, but I think this issue dates back to far beyond the PHB3. I'm surprised that your alarm bells are only beginning to ring now, if you have a real problem with it. WotC have been making up gratuitous new PC races with no compelling roots in any campaign setting throughout the 4E cycle (Dragonborn...), and it was prevalent in 3.x as well (Dromites, Elans, Maenads and Xephs from the ExPHB, and all the new races in the 'Races of...' series). Seems to me like these stemmed essentially from the desire to provide new mechanical options for players, rather than from any worldbuilding impulses.
In any case though, there's really no need to include this stuff if you don't like it. If one of your players is really keen to play one of the new races then you can flesh it out, reskin and refluff it if necessary, and make it a credible part of your setting. If not, there's no need to even think about it.