Warning: Rambling character analysis ahead.
Yes, Zuko was pathetic and weak-minded, at first, but you have to realize why. He had an abusive father, and his mother, who was the only one who protected him, disappeared the night that he heard his father was going to kill him. Meaning, he was left for five years with Ozai, who most likely continued neglecting Zuko during those five years. And Azula definitely would have kept mocking him and cementing Zuko's idea that he was inadequate and a failure. And although Iroh would have likely tried to help Zuko, there wouldn't have been that much he could do for him at that time. Ozai might have banished Iroh as well, if he constantly questioned his parenting skills. So then when he's 14, he's banished and severely burned for merely speaking out of turn, when he was only trying to protect some new recruits.
All his life, he's had nothing but negative things happen to him. So, it's not that surprising that in the beginning of the series, he would act like a villain and a jerk. Yes, Iroh tried to help him, but at that point, he was convinced that he was doing the right thing. He wanted his father to love him, something any person wants, and he can't really be blamed for that. The only problems were that he wanted love from a genocidal psychopath, who probably didn't even love his favorite child, and, the fact that he did this at the expense of alienating his real father figure, Iroh. It's probable that Zuko knew, at least, subconsciously, that Iroh loved him and always would, and used that to justify his constant lashing out at Iroh. It wasn't right but he eventually made up for it. In retrospect, I'm sorta glad he didn't join the Gaang back in Ba Sing Sae. He needed to go back and finally see that he's been doing that he's on the wrong path. It, literally, had to smacked into him that the only person that could restore his honor is himself. This made his final turn towards good all the more satisfying, in my opinion.
About the lightning, didn't Iroh say that you needed a steady mind to be able to seperate the chi and turn it into lightning or something like that? At the time, Zuko was going through a lot of emotional turmoil, so he wouldn't have been able to. Azula's better at bending because she was a prodigy and completely obsessed with perfection. Being groomed to be Daddy's little sociopath can do that sometimes.
So, yeah, that's just my long and incoherent opinion though. TLDR: I think Zuko's quite complex and found his character development to be very nice, not a waste of time. But I totally respect your opinion.
Ahem, so how about that new series, guys?
