Nintendo's target market WAS Young, and casual gamers, and you are taking for granted that being a hardcore gamer means that you must want the best graphics, and it's just wrong.
Games used to be HARD. HARD HARD HARD, like not meant to be finished by most people. and FUN. because back then they didnt have excellent graphics to prop themselves up on (thus having to focus on FUN) and couldnt fit 40 hours of pretty easy content on their media (thus being HARD to extend the life of the game)
IMO true hardcore gamers care about gameplay more than anything. With the Wii U specifically, Nintendo is actually opening up their target audience to include mature (Zombi U, Arkham City, COD:BO2) while games like Mighty Switch Force! Hyper-Drive Edition and Nano-Force NEO will appear to hardcore gamers looking for a challenge.
Don't take for granted that the tablet is a gimmick. Zombi U was unfortunately misunderstood and is an awesome game that makes great use of the tablet, and even ports like Batman and BO2 make excellent use of the tablet controller to provide functionality in a way that can't happen on other systems. On top of that and despite all the fears leading up to launch, Nintendo actually knocked the online aspect out of the park as Miiverse is incredible and much better than I've seen on any other console.
And yes, Devs don't figure out how to properly utilize console hardware right away. 1080p@60fps is plenty for me, now bring on the FUN because that's all I care about