I don't mind the flaming, the post itself was a little inflammatory.
[spoilers ahead]
I have a couple of things in mind. First, I think the casting is spot-on and the actors, including the kids, are immensely talented. The nuance and range of emotions that they can express, as live actors, far surpasses anything that they could do in the animated version. Katara, for example, when she's hopelessly calling out to Aang to come back after he was transformed in Ep 8; the tears in her face, the pleading in her voice when she said "Aang, the world needs you! I need you" really moved me to tears. As did the utter despair and pain in Aang's face when he thought that he had failed the entire world. You just can't get that in animation. The complexity defies the limitations of that medium.
Sure, there are some misses, but overall it's just a better experience, imho.
Second, I think one's opinion of the live action version is highly dependent on the age at which you encountered the original version. I was almost in my dotage when I first watched the show; I watch very little television or video, so it speaks to that version's power that I re-watched the entire series twice.
But I'm not as emotionally tied to it as someone who encountered it in their youth, or early adulthood. Things from those times in one's life tend to become memorialized, immortalized, frozen in that time, and given a cherished spot on one's shelves of memory. So I can see how someone who first watched the show then might be appalled at the changes wrought to bring it to life in a live action format. I mean, how could you possibly have anyone but Katara and Aang in the secret tunnels? It was a key moment in showing their budding affection.
But in the pace of the live action, that just doesn't make sense. Kataang hadn't nearly reached the level at which adhering to the animated version would make any sense at all. So instead, the writers used that to move forward the brother/sister story while at the same time adding to lore that would be needed later. I thought that was clever. I'm sure others thought that was Satan incarnate.
I think you might be biased against animation. The faces of the original show were extremely versatile and well animated. Especially when it came to emotions. Seriously. Check out a few scenes from season 3 on youtube (you could clearly see that they got more budget as the show went along).
From what I've seen up to now, the writing is way worse, completely missing the point of the show at parts. The cinematography is sooo by the numbers. The scenes where Kitara needs to waterbend remind me a bit of Nightboat.
I really wanted to give the live action version a fair shot, but everything but the acting is just so incredibly boooring.
And since they don't even show cool martial arts, it even looks worse that an SD TV show from 2005.
I don't think the ATLA fans are offended by things changing per se. The Mechanist being in Omashu isn't really a big problem. But if it results in an overcrowded episode where Kitara goes from zero to traumadumping in a matter of minutes, you're gonna get valid comlaints. And it still managed to be boring.