Mature games on Wii

In these days a new game was released for Wii: the on-rails shooter Dead Space: Extraction. The latest news (today/yesterday) say that the game has made a really slow start in the stores around the world, selling a mere 9.000 units in the first week.
Now news sites will once again start saying that Wii hasn't got a mature audience, that Wii owners only want casual games, and developers will start worrying about creating new Wii mature games, and shy away (more than they do now).
While I can see the point of the news sites, because I didn't buy Dead Space: Extraction myself and I don't plan to, I don't think the fault of all of this resides all in the gamers and it's not also a blame for the developers. Maybe Extraction is a good game, I am sure they put a lot of effort in it. But come on... let's analyze this.
PS3 and Xbox got Dead Space, a very good game. It sold under 2 millions (at least this is what I can find) on 3 platforms, despite being a good game and a new IP. Wii gets nothing, because it's not powerful enough. Ok, honest. But then? What do Wii owners get? An watered down on-rails shooter, just to say that Wii has got its Dead Space? No, please.
Not to mention the fact that Wii already got two Resident Evil on-rails shooters, and House of the Dead: Overkill (which at least is not an on-railified version of something else), how did they come with the big idea of porting a good IP in a - obviously - cut form on the Wii, and expect good sales?
It already happened with the Resident Evil shooters (placeholders for RE 5), Call of Duty: World at War, and other notable titles which I can't remember now. What did they hope for??
By the way, the same will happen with Call of Duty 4: Modern Warfare. Already on the internet there are image comparison between the Wii version and the PS3/X360 ones. And this doesn't bode well for the game's performance in shops.

Please, developers, try honestly and don't place the blame on the customer.