The Wii does have some hardcore games. The problem is it just doesn't have enough of them in proportion to the rest of the library. The Wii has become the market leading console this generation, but at what cost? The cost seems to be that they lost Ian, whereas if Nintendo had remained in 2nd or 3rd place and struggled to gain recognition Ian and other fans might not have abandoned them. Even though the Gamecube did poorly in comparison to its competitors, who can deny the top-notch quality of Nintendo's hardcore A+ games? The GC didn't have 1st party shovelware like Wii Sports and Wii Play. Nintendo gave us Zelda, Mario, Metroid, and the other usual franchises, but they also introduced Pikmin, Geist, and several others (which unfortunately mostly failed).
This time around, Nintendo's new IPs are just non-game shovelware, and by bundling that with the system as a pack-in that kinda set the tone for the sort of games the system would have. Back in the days of the NES and SNES, Mario was the pack-in and that was a hardcore game so it set the mood for those systems as hardcore systems. Then we had the N64 and GC which did away with the pack-in (at least initially), and that might even have contributed to those system's failures. With the Wii Nintendo has re-introduced the concept of Pack-ins and that's great, or at least it would be great except for the fact the pack-in is a non-game with N64 level graphics. Maybe it would have been better if it didn't have any pack-in at all, or maybe it would have been better still if Zelda TP had been the bundled title. Who can say?
But this softcore tone for the Wii has been further exacerbated by the other non-games Nintendo has been shoveling out. By being bundled with a remote, Nintendo guaranteed Wii Play would be a hot seller and end up in the hands of million's of players. Wii Play, Wii Sports, Resort, and the Balance Board are games that I think have more to blame with the current Wii market than anything else. When you look at sales figures, these games were consistently at the top of the charts and third parties look at these charts just as we do, and that's how they get their inspiration for what they should make.
But I think what 3rd parties don't realize is the only reason those games are so successful is because they were bundled with either a system or a peripheral. It isn't because the market craves these games or because they are awesome or anything; its just because we wanted to get an extra remote and it happened that we could get Wii Play for $39.99 with a remote versus paying $49.99 for just a remote, which made it a no brainer. This inflated Wii Play's sales and made it seem like a huge hit, but Wii Play is just a collection of demos that got played for a few hours and has been collecting dust on player's shelves ever since then.
So we got these games just because of the peripherals/systems, and not because we liked them, and I think this is why 3rd parties are so confused and think the market is chaotic.