I recognize that as a straight male in my 40s there aren't a whole lot of ways i can tactfully add to this discussion, but I'm gonna try anyway.
For starters, the minute you appear in the Sports Illustrated swimsuit issue you're no longer allowed to bitch about people calling you unsexy. It's pretty much a strawman argument at that point. I won't link to the pics because it doesn't add to the discussion but I will assert that Ronda Rousey has crossed into that "can't be called unsexy" realm beyond a reasonable doubt.
BE THAT AS IT MAY
I think the spirit of her argument is exactly what you're arguing - femininity and attractiveness are what you make of it. Self-confidence is far and away the most powerful aphrodisiac and whatever it takes to gain it, do it. Unfortunately we've developed elements of our culture that build up their own self-confidence by tearing others down and beauty journalism is one of the greatest offenders. I feel like the women who hate on Maxim have never picked up a Cosmo... I mean, Maxim is woman-degrading trash but it's got nothing on Helen Gurley Brown's monster. And the mags are all about what's "sexy."
They sell magazines by making you feel insecure, and then make you feel better by doing what they say. That's engagement and brand loyalty rolled into one. I agree with you - it's a crass method to follow but they're aiming for the lowest common denominator. Accept that you aren't fourteen, that their arguments are beneath you and don't give them the leverage to get under your skin. Whenever someone with something to sell tells you "x is sexy" just remember that they're just trying to make a buck off your insecurities.
And then don't let them.