Time travel is mostly used as a deus ex machina to solve a problem a weiter has written themselves in. Like in HP, Therme ia time travel bit only for students or to learn more, not to erase attacks by Voldemort, because reasons. In other words, they could have stopped the death if Harrys parents, but did not want to, because reasons.

I get rhat if used well and as a consistent plot device, it can work. But in HP, its simply a one oft drama device. Its boring and lazy writing.

Edit, ah, I see

My Immortal is popularly regarded as one of the worst works of fan fiction ever written