This guy explains it better than I ever could, which is probably why he writes for The Atlantic and I write...well...here.
http://www.theatlantic.com/entertainment/archive/2013/12/-em-love-actually-em-is-the-least-romantic-film-of-all-time/282091/
As for the rest of the film—which is to say, the bulk of the film—I think it offers up at least three disturbing lessons about love. First, that love is overwhelmingly a product of physical attraction and requires virtually no verbal communication or intellectual/emotional affinity of any kind. Second, that the principal barrier to consummating a relationship is mustering the nerve to say “I love you”—preferably with some grand gesture—and that once you manage that, you’re basically on the fast track to nuptial bliss. And third, that any actual obstacle to romantic fulfillment, however surmountable, is not worth the effort it would require to overcome.
Begin with the elevation of physical attraction over any of the other factors typically associated with romantic compatibility: similar likes and dislikes, overlapping senses of humor, shared values, what have you. Grant falls in love with McCutcheon the first time he speaks with her—“Get a grip,” he chides himself moments afterward—when essentially the only thing he knows about her is that she accidentally uses profanity a lot. (Charming? Sure. Evidence of a soul mate? Unlikely.) Firth and Moniz, meanwhile, fall in love despite not sharing a word of language in common. Moreover, the movie telegraphs very clearly that the moment when Firth really falls for Moniz is when he watches her strip down to her underwear."
I know, I know...me? A romantic and a defender of romantic love? I surprise even me.
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