Okay so kicking of NATLA reactions. The telling not matching the showing. The time skip was necessary and unavoidable and with kids having growth spurts it DEFINETLY needed to be mentioned. It's the koalaphant in the room. Well and good, there is a place for telling and the way it was brought up was cute.
My problem lies with everything we we're shown contradicting the amount of time that was skipped. Aang has been learning waterbending for a while. Katara shouldn't need to manually adjust his stance. ESPECIALLY when a chunk of the season is trying to convince me that he's having a hard time with earthbending-- yet overall it's clear he picked up on it MUCH faster than two years. They could have had Katara nag him a little or instead of him learning to heal being one scene make that a bigger plot point, spread out the attempts. Healing is a cool idea for him as a character. Maybe have Katara go to stop him from healing the serpent or be like "woah you're gonna do it wrong and make it worse" or even "wait we gotta make sure it doesn't wake up if we're going to do this." SOMETHING -- these are all quick ideas but at least they're SOMETHING. I could see Zuko spending a few months before getting restless about the fieldwork and running off. With the way his dialogue is setup and Iroh explaining to him why they're there over and over again it feels more like two months no matter how much they try to verbally convince me it's been longer. Why not just start the season with Zuko on his own and imply he was own his own for longer? His desperation would sink in better and he could be shown looking for the Avatar since we're supposed to believe he hasn't let this go. You could have Iroh trying to track him down. Even the interpersonal conflicts between the Gaang don't seem like the sort of conflicts that would happen if all but one of them had been around one another for years. The fix isn't even complicated, make the issue not be trust but be "hey being in the city is changing you"