Just out of curiosity: how familiar are you with Doctor Who? Are you 'just' a fan of the new series, or are you a fan of the classic series as well? I'm not trying to say that you're not entitled to that opinion if you have/haven't seen the classic series, but I'm just curious what your perspective is.
For me, I got into the series with Ecceston, watched it on and off during the RTD years (while I liked the concept, RTD's vision of the show doesn't match mine), and I fell in love with the series during season 5. I went back and watched all (all) of the classic series, and these days I guess I'm a bigger fan of the classic series than the new one. I was actually one of those people that was secretly hoping to see all the (living) classic doctors show up, but in the end I'm kinda glad that Moffat chose story over fanservice. John Hurt worked perfectly for me, because he both represented the idea that the show should always feel new, suprising and familiar at the same time (while presenting some light sci-fi/philosophical ideas). The way he talked and presented himself felt like a great representation of the calmer, more eloquent classic Doctors, while avoiding the awkwardness of, for instance, the 6th Doctor showing up while he's noticeably older/fatter/CGI/played by someone else. None of those scenario's would have really worked, I think.
Just as an example, I loved the small moment in the beginning where he's mumbling over the box containing the Moment, wondering about a big red button. It's not a joke that makes you laugh out loud, but it gives a sense that he still has that same sense of humour that the Doctor has always had, both in the classic series and the new one, but with a sense of weariness that the war brought. He totally fits in with the rest of the Doctors for me. Keep in mind, while 10 and 11 are often dancing around and waving their arms, most of the Doctors where never near that 'manic'. He bridged the gap between the classic and the new more than McGann or Eccleston would have done, for me.
Anyway, you're obviously entitled to your opinion, but I loved his addition and he is a big part of why Day of the Doctor is so memorable for me. I still think it would be nice if the other classic Doctors would have gotten a small part (even if it was just a couple of shots of them saying couple of lines while in their respective Tardises in the big scene at the end), but taking the story for what it is I think it's one of Moffat's best.