I agree so much with your opinion. Beside, they conveniently forgot that he didn't wait for Jieun to come to mistreat her.
First timeline and beginning of second timeline, the Duke was close to the Prince, literally pretending to be friendly to him since everyone was distant towards Ruve. Fed him poison about Tia, so Ruve would come to hate Tia. It was only in second timeline when Tia first got hurt and Ruve went to see her they have their fallout. And Ruve was no longer in the Duke's grasp. He continued his second plan to use Jieun as a puppet and actually poison Ruve so he turn to a tyrant emperor and eliminate him when he become the grandfather of the crown prince.
...Or blame some never-before-mentioned villain mastermind to deflect blame from Ruve. The duke may have influenced Ruve into hating Aristia, but Ruve was the one who chose to hurt her (and then execute her). But I guess Ruve is not completely at fault. Aristia has an unhealthy love for a man who hates her. She said she wouldn't fall for him again if she were reborn, and when she spoke with Vita, it was suggested her feelings for Ruve were not her own. (Like she was only meant to be a placeholder for Jieun? Whatever that means) In any case, Aristia said she was going to fight her fate and so she was granted the name Pioneer. But ending up Ruve would basically be her replacing Jieun this time around, and that isn't much better than what happened in the original timeline #－.－)
I don't like that the prince gets an out and both women have to suffer (one in each timeline). But since we're reading from a particular point of view, we don't want this FL to suffer. Honestly, we need one more reincarnation where all the shitty men get killed and the women get to live happily without them.
People like to place all the blame on Jieun, but I think that's a really big cop out on the author's part. Like, ofc blame the other girl! (And you know what, let's make her so unlikable and the ultimate villain in this new timeline just to reinforce how good and different Ruve is now!). That way we can forget everything Ruve did and hope he and Tia get a happily ever after. If any of these two girls had any common sense (or like a neutral party who is looking out for them), they would throw the whole man away. You can say he is different, but he only notices Tia NOW because she is suffering from his actions that he himself inflicted in another timeline. She has PTSD and recoils from him in the earlier chapters, but we're supposed to think it's okay if they end up together because they love each other? No, any relationship they could have is irreversibly doomed because Tia has memories from her past life that shape who she is in this new timeline.