This is an overstatment, perhaps, but I think the attraction or mystique of Spock to women fans in TOS was that he was both highly desirable and seemingly unobtainable. He was a distant, cold figure. And lonely. A woman may be tempted to think, "I know that's not really him, and if I had the chance, I could break through and get to him." In the show, that was personified by Nurse Chapel. In the end, Spock represented unrequited love, which probably even added to his attraction. Whether or not one likes the idea of Spock having an open relationship with Uhura or not, thematically, their relationship changes that TOS image of Spock. The mystique is gone. The attraction of unobtainability is gone. And so is unrequited love. Instead, it's about Spock learning how to love, and Uhura gets the chance many female fans may have fantasized about in the 1960s. This Spock is not lonely.