I can't speak for the general public, but as for the nerds (ok, specifically for me): probably because the new movie was not on par, either in style or philosophy, with the 1995 movie?
The total running time of the remake was more than the original movie, yet somehow said a lot less. Aside from the visuals, the movie was embarassingly mediocre.
Sound was good too. Can't recall what they named the antagonist, but failed experiment dude's voice was 10/10. Such a perfect addition to sell the "this is one fucked up Android" message.
And that is where they went wrong (the nerds that is). This is a new work, you should evaluate it on it's own merits and not how it compared to a artifact in what is essentially a different medium.
It's almost as if many critics forgot about all the different versions of GitS. Starting with the manga.
When the first movie came out people were complaining that it is not the manga. I'm pretty sure if they'd made a 1:1 copy of the 1995 movie, the same people would complain about that.
There is no way to please everybody. People will find reasons if they feel they need them.
It's true you can't please everybody, but at least in my case this doesn't apply: I own both the manga by Shirow and the movie by Oshii, and absolutely prefer the movie -- in fact, I don't like the manga very much. Back in the day I didn't complain the movie by Oshii wasn't like the manga, I celebrated it because it was so much better! Likewise, the new movie fails not because it's not exactly like the classic '95 movie, but because it's not as good as that movie... and makes me wonder why it was needed at all.
Well, this "as good as" is more of a personal opinion though.
I love the '95 movie. It was the first anime I watched and it showed me that there is not only tentacle porn and little girls there. But I've also seen everything else that was branded GitS and I have the manga here. Therefore I liked the movie because it was just another interpretation of the general idea that is GitS.
Because of that, I find that harsh and kind of orthodox criticism quite over the top.
I didn't like it not because of previous work, which I haven't seen in ten years, but because it was hamfisted. Scarlett's acting and the "moral of the story," shoved down our throats with no subtlety. Luckily other characters absolutely slayed it.
