Why does Korra lose so much?

So I'm watching the Legend of Korra for the first time and I really like it, it's not as good as the previous series but it's still a solid 8 or 9 out of 10 for me. But an issue I have with this show is Korra in fights. At the start of the series she has mastery of 3 elements, on paper she should be extremely op, but she's always losing in fights constantly.

Throughout season 1 she pretty much gets slaughtered by most opponents shes faces like Amon or Tarlock. Up until the last episode where she somehow breaks out of his bloodbending with just airbending. And in season 2 she literally gets beaten up by her uncle and the evil spirit dude so badly that she loses her connection to the previous Avatars. In season 3 to be fair she is poisoned in her fight with Zaheer, and it is pretty clear that without the poison she would have beaten Zaheer pretty easily. And now I'm on season 4 and she's so weak and rusty that she can't even stand a chance to Toph, someone who Aang beat with only airbending mind you. But hey, she's weaker because of her personal trauma or something, fine I can buy that. But she gets over it once she removes the poison, so that should mean that she's back to her former strength, if not just slightly weaker, but nope. She fights the evil metal bending girl in a 1v1, (I forget her name) and she doesn't even stand a chance, what the hell. No matter how rusty she is how the hell is she losing this badly to a mere metal bender, she's the Avatar, master of all 4 elements and you expect me to believe she can lose to the uniter, Korra can barely even use the Avatar state either wtf.

I hate to play the comparison game, but you can't tell me Aang wouldn't effortlessly defeat this metal lady. Not just Aang but Avatar Roku or Kyoshi would slaughter her as well, or just about any Avatar for that matter. Korra looked so strong at first but it all just goes downhill from there.

This isn't to hate on the show. Because again, I really like this show, but this is just something I can't ignore. I know that she usually has handicaps in these fights, like the poison with Zaheer, or being rusty but come on man...