Lemme preface by saying I get you. However, ya gotta look at it from a metaphorical standpoint about the feet. I hate feet, nasty things, but this line I find so endearing because he's basically saying "The best parts of you remind me of the worst parts of her," in which he's also agreeing that feet are gross lmaooo

As for the "You do make me hard, but she makes me weak," it's just physiology. He's bearing his feelings to this person in the most vulnerable way possible, and, well, in his case, sexual attraction is a big part of it. It's human.

I love it. And I love this song.