1) The character changes. First off, Zuko is a crazy war obsessed nutter again. This really upset me because at the end of TLA Zuko's character definately semmed like he had matured from that anal teenager into a fully realized firelord who wanted to make the world a better place. But for some reason they thought it was neccessary to take Zuko back to his old roots so they could jam in the fact that he is CLEARLY confused and is struggling to do the right thing (yeah, because we clearly haven't gotten enough of that in the past) and go through yet another character arc where he realizes his mistake and tries to better himself in the future. I'm sorry, what was the whole point of having him go back to an angry jerk again? we get it, Zuko has struggled in the past. But by the time TLA tv series was over he seemed totally matured and was ready to live a life of blissful happiness and unquestionable honor as the firelord. So why did they make him convert back? I don't really see the reason why to be honest. Just more dumb character arc like we've never gotten before (sarcastically) and Ozai I thought was especially bad. He went from being a ruthless tyrant to somewhat like Iroh... While Zuko was visiting him in prison he asked him to bring him some tea and he even gave him good advice on how to be firelord. He told him that he can do what he wants because he's firelord. I would of expected Ozai to be more like "You don't know what kind of power you harness and you are yet to realize the responsibility of being the firelord. Even now you are still weak. You do not deserve this power" now doesn't that sound more like Ozai?
2) Potential drama? Okay, so it's obvious that Bryke is teasing us with this whole Mai and Zuko thing. And again, I ask. What was the point of making them break up again? When ATLA ended I really thought that Zuko and Mai were going to have their happily ever after. And I was happy for them despite my deep hatred for those two being together (I was a huge Zutara fan back then) so having them break up should of somewhat, redeemed them in the eyes of myself and other Maiko fans at least. But honestly, it makes me even more frustrated because I know that they are going to get back together eventually (even if they end their relationship permanently on a positive note) and it will be another dumb character arc moment when they realize how much they mean to each other and how they make each other happy. I mean come on, how many times do you think your gonna fool us with this? it's obvious that they care about each other so why don't you just make them get married already? Why do you feel that more teen drama is neccessary? It's not intriguing in the slightest it's just causing more senseless drama across the fanbase. Which yeah, I get it... is kinda the point. Well done guys, someone oughtta give you guys a tediously obnoxious producer award.
3) Characters are somewhat uninteresting in this, reading perhaps? So yeah, if your gonna go through the effort of bringing these characters back one last time then why couldn't you make another series or why couldn't you extend the original series for a couple of more episodes? or even brought them back in flashbacks like in LoK? Maybe it's just me but I really don't like the fact that they continued the original series in reading format. It does somewhat, take alot of the humor out of what made the original show so fantastic and one of the greatest tv series of all time. Sokka still has his sense of humor, great... But what's the point if you can't hear Jack DeSenna's hilarious voice dubbing Sokka's likable sense of humor? It just takes away a huge element of what made Sokka so funny and likeable in the show. But I do give him some credit though, at least he was funnier than the 2010 film.
4) There's no reason for them to exist. When ATLA ended, that was it. Aang and everyone elses story was complete. We know that he formed republic city after the 100 year war was over from watching LoK. There is no reason to carry on what was already perfect. The tv series ended on a positive note like all good tv series should. So when I saw Katara and Aang kiss in the end, I genuinely believed that they would be together forever. And I was right, same with Mai and Zuko when they got back together in the end. But apparently not :/ we don't need to know every single detail about what happened when the war was over. That's just backstory, and the whole purpose of backstory is that well, it's pretty much pointless xD. Everything was summed up in the very beginning of LoK. They explained in the very beginning that after the war was over Aang and his friends formed republic city so that all nations could live together and even non-benders. That's all you need! You don't need to justify every little detail that happened in the process of the harmony restoration or the process of bulding republic city. I do believe there are some redeeming qualities of these comic books. The first is that we do find out what happened to Zuko's mom and it's about god dam time too! But why couldn't you have put that in the show like I mentioned before? If it's the limited episode quantity your worried about then why couldn't you of just cut a few other episodes out? I can think of a few. Like, Appa's lost days, Tales of Ba Sing Se and all of that other stuff. We don't need to know every single detail of what happened to the Avatar's bison when he got captured but we DO need to know what happened to Zuko's mother!!
So yeah, this is just a few reasons why I hate the promise trilogy and most of the other comics too. Keep in mind that these are my own thoughs so don't go ape shit if you don't agree with me xD