Like all things Game of Thrones its such a fucked up implementation that its not seen as a viable long term solution (similar to magic). So as opposed to other time travel ideas in other shows/movies its less about cheap plot shortcuts/seeming smart but fleshing out the world and how fucked up it is.

Dude broke his friends mind as when he was child leaving him brain damaged and on top of that doomed him to an eventual fucked up death. This aint Back To the Future Nike kicks.