Subaru should end up alone, he doesn't deserve to be loved by anyone
He loves Emilia because she was the first cute girl to give a fuck about him
He loves Rem because she was the first cute girl to show affection to him
Subaru admitted himself that he would have gladly accepted Crusch's feelings if his heart wasn't full already, and mind you, he interacted with Crusch for, like, two days at most and half of those interactions were her being polite to him and telling him to eat shit and die in the failed loops
We have direct confirmation that Subaru would have fallen in love with Emilia in any fucking scenario because he falls in love with her in their first interaction in Arc 6, and the reason for this isn't because of destiny or because of her silver hair, it is because she was CUTE and NICE, that's it, that's how low his standards are, he is basically a duckling that follows the first human being that fills those checkmarks.
Anastasia and Ram are way too bitchy for him, so he didn't give a fuck about them
Beatrice looks way too young for him, but she was cute, so he half gave a fuck about her
Shaula was way too slutty for a japenis boy, so he kept her at arm's distance without entirely pushing her away
Subaru could have fallen in love with Crusch, Yae, Theresia, Elsa, Satella, Ram, half of the witches or anyone else that acted as if they gave half a fuck about him because his self-esteem is that low, and he deserves to be alone until he learns to differentiate horniness from gratitude from love.