I agree! We don't have enough of the characters in depth persona in the manga. It's mostly just fluff (and the angst that was in the intro but was not explained much in the ending). Hero would explore profound this like this but I don't know if it had closure
Yuki is explaining her inability to actually commit to liking something. She wants to be with Tooru, however her overthinking prevents her from loving Tooru as she is constantly considering infinite possibilities. She also is saying that there's no purpose for love, because there is no exclusivity of doing things when in love, thus her metaphor of rape.