MC has some of fault here, but he is also not totally wrong. He is afraid to deviate the story that much from the original because that would mean they will have to deal with an "end of th world scenario" withou the necessary means to stop it.
Livia needs to find "True Love", as cliche as it sounds, because that its one of the requisites for her to unleash her power, but AT THIS POINT of the story, he can't become said True Love because there are many barriers between them, both emotional and social.
So, if HE can't be her True Love, then he had to step aside while trying for Livia to find love with one of the original targets, because they should have the highest chance to attain it.
Yes, things change later in story, but again, AT THIS POINT, its a really high risk, not only for him, but for the entire world, if he try to become Olivia's lover.
But that is just my opinion.