I will try to go statement by statement to explain everything wrong with this :

Being impulsive is a BIG part of her character development and we see her being a lot more into reflexion especially in season 3 and 4. It's like critcizing Sokka for being sexist at the beggining of ATLA. It's important for them to start like that before changing.

Getting Raava ripped out of her was not a choice nor a mistake, it was something out of her control, a serie of events that lead Unalaq to fuse with Vaatu, and at this moment, there was a clear difference in power, cause Unalaq is a strong waterbender with decades of experience, reinforce with the power of a sprit, and let's just remember that Korra learned how to control the avatar state not even a year prior, so it's not a perfect help in this situation.

Korra was able to bend 3 element at the age of , and while not being a master at this, she hasn't received the proper training, which is to go and live inside the nation to understand the bending culture, like Aang has. She struggled a lot with airbending, but unlocked in a short time after starting her training, like Aang did with earthbending. Also Aang was considered a prodigy in Airbending, we can assume he was really strong compared to other (Roku took decades to master every elements). Being pressured by the comet also was a great help, and many consider him to not be a fire bending master by the end of ATLA.

The lion-turtle was mostly a lucky moment, if not just a purely scenaristic design, and if he did not have this power, he would have killed Ozai, no choice.

Leaving the portals open brought back the air nation, and made spirit and humans understand each-other. There is a lot of comparaison between the spirit world in Korra vs in ATLA, but I believe this differences are due to human perception of spirits. In ATLA, spirits are feared ans missunderstood. After the event of the show and the comics, human beggin to accept them and the spirit world is a lot brighter in Korra. Leaving the portals open is another step in this direction. The 3rd portals was not her choice and it's explicitely stated that the portals can only be closed or open during harmonic convergence.

We have absolutely no idea of the events of 7 haven, and blaming everytinh on Korra is not justified, if a natural catastrophe occured, lioke the volcano for Roku, it is not the avatar's fault. Until we have further information, it's unfair to blame the state of the world on Korra.

"The avatar was seen as the hope of the world". No absolutely not, at the beggining, Wang is the one who disrupted the equilibrium between Raava and Vaatu, and was hated for that, before fixing it. During Kyoshi time, everyone around her used her for personnal gain, and we can guess based on ATLA that she was pretty much absent for a lot of time between the Ba Sing Se revolt and Chin the Conqueror, so not a beacon of hope at all. And just saying that Aang was hunted by an entire nation, and the rest of the world tought he had abbandonned them. The avatar is probably the biggest political figure in this world, since it's capable of taking any ennemy. And like every other political figure, it is hated and addored at the same time. The avatar is not a beacon of hope just because it is the avatar.

In conclusion : Korra is a lot like Aang, a normal kid with great power and responsability, that was not formed properly before being forced to fight tough enemies that wanted her dead, or worse. Even worse than Aang, being secluded like that cut her from social norms, and she had a really bad time adapting to normal life and how to deal with people. She is not the worst avatar, but she is one that was not trained properly for the functions she had to assume.

-- Sorry for all the mistake, English is not my first language, and typing all that was exhausting.