Zutarians will point out the toxic behavior of A/a/ng in Ember Island Players and correctly point out that he's being pushy and possessive and entitled, and the Ka/taan/gians will counter by bringing up the Beach episode and how Zuko acts in it as a way to say "See! He's way more possessive and jealous with his girlfriend!!"
But they seem to miss the crucial detail that the Beach episode is meant to be Zuko at his worst, the peak of his identity and morality crisis that has him acting like a jerk. And he IS acting like a jerk in that episode, but we're clearly meant to understand that he's being a jerk and the narrative punishes him for it. Mai breaks up with him after calling him out on his anger issues, and good because someone needed to put their foot down (my fellow Zutarians give too much flack to Mai in this episode often, like she might've been being not the best girlfriend earlier that day, that's debatable, but she was valid for calling him out on acting like an angry lunatic) and give him consequences for his actions.
It's a good thing that Mai was willing to stand up to him and call him out when she knows she's being treated unfairly, and for knowing her worth enough to not take him insulting her. Then they get back together only after he actually opens up about why he's angry and admits that it's himself he's truly angry with.
But again we're meant to see Zuko's behavior as bad in this episode, the whole point is that he's lashing out at everyone around him and is angrier than he's ever been because the guilt of what he did is eating him alive and instead of dealing with it in a healthy way he's taking it out on others.
And even more importantly, Zuko stopped being angry and belligerent and violent, this was the sort of behavior he left behind when he decided to do the right thing and work on himself.
There is no reason to think that post-redemption arc Zuko would act like this again with a girl, because the only reason he was acting like that in the first place was the inner turmoil he had yet to work through, caused by his betrayal of his uncle and what he knows in his heart to be right.
He actively worked to improve himself and be a better person, and to be less impulsive so that he wouldn't hurt the people he cares about.
Everyone always agrees Zuko's redemption arc is one of the best things about the show and loves how far he's come, until it's about Zutara and then he's actually stuck as the worst version of himself forever.
The difference between how Zuko is in the Beach episode and how A/an/g is in Ember Island Players is that Zuko is punished by the narrative and we're meant to see his behavior in a negative light, he is forced to atone and change. A/a/ng is not forced to atone or change for his bad behavior and it's unclear if we're supposed to condemn him for it or if we're just supposed to feel bad for him for feeling bad.
Comparing pre-redemption Zuko to A/ang at any point is not a fair comparison, if we really want to compare their behavior to assess the kind of person each of them are, we need to look at redeemed Zuko if we're going to compare him to A@ng.
It's just funny how trying to make Zuko look like a bad person or like he'd be a terrible partner only works if you pretend the redemption arc never happened.