Realism has never existed in a pure form in the Zelda series at
any point. The original Zelda games' artwork had a grim tone but always a very cartoony style despite that, with the exception of the scene artwork done for Adventure of Link and Link's Awakening (seen
here and
here), but while those were far more realistic they also had their own stylization, with an almost over-grimness and limited color schemes to create an unusual effect. These were the only real grasps we had of those games' art-styles, since the games themselves were sprite-based and simple.
With Ocarina of Time and Majora's Mask, the games segued from a more traditional cartoon feel into an anime feel, with more detailed environments and semi-realistic characters that still had cartoony aspects and were overly-expressive in the way that anime characters are. This is consistent between both the 3D models and the official artwork for both games. The Wind Waker took this farther, combining the super-deformed or chibi style with a bit of the classic cartoon vibe and more or less reverting back to the look of the original games but with its own spin on it (whereas the Game Boy titles mimicked A Link to the Past and the DS and Game Boy Advance titles mimicked The Wind Waker). Skyward Sword mimicked Ocarina of Time's anime feel -- stylization blended with a degree of realism -- with its own spin on it, while Hyrule Warriors is clearly doing the same thing.
Where I am going with this, is the series has no real precedent for being realistic. You ask "why is realism bad", but to put it bluntly, it doesn't matter whether it's bad or not; it's just not within the series' identity whatsoever. I imagine a number of Zelda fans take to it sourly because it's not what they look for in the series; it's not what brought to the series neither is it what keeps them playing it. There
isn't anything wrong with realism on its own. But trying to say the Zelda series should be realistic is unavoidably a very sudden shift that is contrary to nearly its entire history up until this point. People not wanting to see the series drop its stylization should not be surprising whatsoever; it's to be expected.
As for Twilight Princess, there are three important things to note about it:
- It is not realistic.
- It tried to be.
- Its identity lies in its grit and dullness, not its realism.
Twilight Princess
isn't actually realistic in general. It's still very much a blend of stylization and realism, like Ocarina of Time, in that the proportions of the characters are often still quite odd, with anime facial expressions and other quirks. However, there is really no doubting that the game was going more for a realistic look. The environments are hyper-realistic barring console limitations, and there's a higher ratio of believable to semi-believable anatomy than there is in the other anime-styled games in the series. The Call of Duty comparison that some people make -- I've never made it myself -- I believe stems from the fact that Twilight Princess was an awkward execution of realism; whichever artists worked on its visuals, they decided that being realistic meant they had to subdue the colors, mute everything, and make the entire thing visually dull.
This is a poor representation of realism and also horribly muddied the stylized elements of the game. The real world is not that drab, and has more striking color. Pulling out and exaggerating things in your game's art -- stylizing it -- has a lot of neat advantages, but is damaged by not doing similar things with color. Put plainly, Twilight Princess lands in an extremely awkward and bad place between realism and stylization.
It's a bit sad because Twilight Princess is actually very similar to that scene artwork from Adventure of Link and Link's Awakening, which was cool stuff. If Twilight Princess' developers had tried to keep visual flair in mind more, it could have been a much better-looking game than it was. As I said before, those scene pieces has exaggerated and limited colors, and aren't Twilight Princess' most striking moments ones with lots of contrast between just a few colors? Link and King Bulblin battling in the sunset, Gerudo Desert at night, the Light Spirits shining in their springs... these are moments I found beautiful in Twilight Princess, but all of them involved creating contrast through awesome lighting; apart from moments like these, Twilight Princess has very little contrast, and that damages both its realistic and stylized elements. With regards to the gritty aspect I mentioned earlier, many things in Twilight Princess are twisted to be made disturbing; just look at the enemy designs and the general tone of the storyline. For some that's cool, but again remember that there's a more whimsical tone to most Zelda games; even the horror in Majora's Mask is set in a dreamlike and surreal world, not a harshly, ugly realistic one. There's a big difference in tone between the ethereal and oddly gothic
Gomess and the realistic ugliness of the
Deku Toad.
Now, me personally, I'm with the crowd that grew up with the series. I've never known Zelda to be a realistic series, and I have no interest in it being so; I play realistic games and stylized games, and I enjoy both, but I don't see why Zelda needs to change because of some silly new idea people have about how it should be realistic because... What, because they missed all the anime influences in Ocarina of Time's visuals? I don't mind the series making attempts at realism, but they have to be well-executed and they can't completely deny stylization, whimsy, and
vibrancy. If you don't keep those elements intact, I feel you're just sucking the life out of Zelda. Zelda has never been realistic fantasy. There's nothing wrong with realistic fantasy, but that's not what Zelda is. Zelda's always been a bit silly and a bit odd. Don't be surprised when people are bothered by the idea of that changing.