Have you seen the attach rates for NSMBU?
Have you seen the attach rates for most Nintendo IPs on Gamecube? Nintendo always lands big attach rates with their main character IPs. That doesn't move consoles to anyone but dedicated Nintendo fans.
And also, are Wii levels what it takes to be considered a successful console? Because if they are I guess we won't have many successful consoles this generation. If any...
Wii levels are what it takes if you're going to lose money per system out of the gate, yes. Otherwise you're selling a big chunk of your first party software just to recoup your losses.
That's the rub here. If Nintendo released the Wii U at say, $250-$300 without the tablet and where breaking even on the hardware from day one this would be a different discussion. They could always just have another Gamecube and be profitable within their 20M user walled garden.
Instead they chose to go with a loss leader system in order to push the tablet. Now instead of making profit on the first game sold they need the first game or two to just get back to even. That has long term ramifications as they can't keep the current MSRP without hitting a point of complete stagnation, and the manufacturing price of those tablet controllers won't come down fast enough to keep them from losing money throughout much of the Wii U's early life.
The 3DS was a shit design by Nintendo standards because they couldn't sell it at what it cost to make. They had to lop $80 off the MSRP and take a bath to get it selling at GBA levels. That was for a product about to receive major Nintendo IPs, meaningful 3rd party support, and following a global defacto standard handheld without any feature loss. The success of the 3DS will be meaningfully diminished over it's entire life because of that.
The Wii U is even worse off than that because it likely doesn't have a rebound of meaningful proportions in the cards.
This is why Nintendo needs to stop making two hardware products. It fractures their userbase, making them spend money on two different loss producers to get all Nintendo games. It fractures their development teams, making them have to focus on Wii U or 3DS titles.
They need to consolidate and deliver a single device. A powerful handheld that doesn't go overboard on ancillary features with the exception of HDMI out, likely a wireless HDMI out.
In about 5-6 years time (when they should make this move) a PS4 level handheld with a generic version of Intel's WiDi (or even Intel's solution directly) could likely be produced at a $250 price point and break even. It'd come with the system and an HDMI dongle. Have a pro pack for $300 that includes a wireless controller based on the Wii U's pro controller and a dock. Release an optional optical drive accessory for the dock to give GC/Wii/Wii U BC if you really want to.
That product would compete incredibly well with any smartphone competitor and would unify the Nintendo fanbase onto a single format to maximize software profits. They don't want to compete with Sony and MS in the hardware race so why even compete over the same niche in the industry? Make your own niche that completely fits with Nintendo strengths (offering superior pure gameplay, no bells and whistles needed) and ideologies (weaker hardware so as not to lose money per unit).
Stop being something you're not. Stop trying to catch a fickle market that only randomly exists. Serve your core better than they've ever been served before all from one format and they'll evangelize that specific format for you to everyone they know.