
My personal top four reasons I am not a fan of the ending is:
1) because it is like saying that Tia was responsible for her fate in the first timeline and that she needed to fit Ruve's taste better to get her happy ending (not the message that the author wanted to convey but this is how I undertood it)
2) That while PTSD can be overcome somehow and that in the story years have passed (so Tia could reasonably be mostly healed by the time we reach the middle of the plot), the reading of the books and manhwa is quick so we get a feeling of "trauma magically disappearing". Especially with how brutal the mistreatement she suffered from in the first timeline was. It felt unnatural
3) There is a better option as the ML. Some don't mind Yandere and will go to Allen. Some will go the Carsein because he is the most reliable and true caracter of the three. Tia was traumatized by Ruve then healed thanks to Allen and Carsein. Allen being psycho and wanting to use Tia most of the story explain why she won't choose him. But it is more difficult to explain for Carsein. It was a love story waiting to happen. Ruve getting the girl when he had the less screentime of the three was a bad decision, because by then most readers just could'nt get other Carsein who was basically without fault if only of not confessing properly. A better path would have Ruve curious of why Tia was so terrified of him, sending her letters and over time slowy reaching a friendship turning love. In the manhwa and in the story they were never friends, only "ruler and subject", so it felt forced to me that he suddenly fall in love with her. And if you call it "fate", Tia was supposed to be free from it has a gift from God. There were not suposed to be "fated lovers" anymore.
4) Ruve hated Tia at the start of the second timeline without any reason other than jalousy and rumors. He took it on a 9(?) years old when he was much more older and was expected to be "rational" and "adult". He got angry at her from nowhere just because she knew his tastes in food of all thing. Then, out of nowhere he has fallen in love with her... I get it, everything is from Tia's POV, Ruve is not t like that, there is a reason for everything and all... However, exactly because of that Ruve come accross as intitled, deserving to get the girl even if she is willing to take a blood oath of servitude to get away from him.

While I can agree that they did skip over a lot of PTSD, that still does not change the fact that this timeline is Tia’s do over. She lacked almost everything in the first timeline aside from being queen material and there was no chance for her in the first timeline. Especially when you consider that the first timeline was a technical mistake since Tia was marked as the blessing or whatever. Plus there were other details within the novel that wouldn’t fit in the manhwa but there were explained reasons, not excuses, for Ruves behavior. Like it or not, Tia grew not for his sake but for her own and that is what attracted Ruve in the second timeline. Honestly? Could even explain the PTSD recovery as she has more social support than what she once had.
I’m gonna ruffle some feathers with this I’m sure but? Some commenters seem to forget that this isn’t the prince from the “past,” this is the prince in a whole nother time line. The two are now independent existences that only coincide due to Tia and Jieun. This also means that the prince might as well be a separate version from the other time line and has overall acted much differently than previous timeline. Holding the separate timeline prince over current timeline prince’s head holds no water. What he did in the other timeline was despicable and there is no excuse for what he did but he is, quite literally, not the same person.
He had the potential to be the same person, but due to Tia’s actions he is not following the same path.