I hope none of you here takes "waifuing" seriously. I mean, jerking off and fantasizing about fiction is okay, but if you're insisting that a person can only have one waifu, or something similar, you're delusional. Let me explain.
Your romantic partner is supposed to be your soulmate, someone you're comfortable with. And it's hard enough fighting a soulmate in the real world. But at the very least, in the real world other people share your goals. They, too, want a comfortable relationship with someone. It's one of the things that makes you both irrational human beings: each does a lot of random, seemingly nonsensical actions that don't have any real closure.
With waifus, the romantic partner doesn't share your goal. The only goals of your romantic partner are 1) to express an idea that exists within the context of a work 2) to be expressive, interesting to follow and superficially attractive. In this way, fictional characters are way more rational than us. Their life has a meaning. Whatever a character does, it's a dramatic part of some character arc, with the endgoal to change them in some way that helps convey the part of the overall message behind a work of fiction.
That's why it's hard to waifu characters from finished works, such as books or movies. With them, the narrowness of everything they do is more apparent. Them existing outside of a certain context is impossible, because they are a part of what makes that context. But last decades gave us such a thing as a media franchise. It allows to tell more than one story within a work, but it also allows to create of illusion that a character's life is similarly meaningless to our own. Hell, sometimes it actually is, like with pic related. But at the end of the day, they're still characters, and whatever happens to them is still supposed to be fitting for a story. That's why they'll never be your soulmate. Their endless "life" has meaning, your limited life does not.