The reductionist biological explanation might be obvious to you, but in the actual world, the reasoning and the moral condemnation of things like plastic surgery is never explicitly about giving false signals regarding one's reproductive fitness. Reasons "haters" cite are about vanity, narcissism, refusing to look your age, etc.
For me, motivation matters. If you want to learn social skills to make your life easier while not harming others, that's perfectly fine, admirable even, but if you learn it to damage others for your own profit, that's immoral.
Same for the motivation of surgeries. You might not be comfortable with yourself, and want to change something, and that's perfectly fine, but again to changing appearance signal something to benefit you and harm others with less effort, it's immoral again.
And, I believe, if you need to change how you behave or look to get acceptance from a circle, this means the circle is toxic and you'll be far happier elsewhere.
To me, a big factor that I subconsciously evaluate on is the "fakeness" of the appearance itself. Instances where plastic surgery results in the uncanny valley of "should be good but looks too perfect or messes up a critical aspect" disturb me. Plastic surgery isn't as powerful as Photoshop. Maybe that's more on the surgeon, and subjective criterion of attraction (such as mine), but it simply isn't the case that plastic surgery makes someone look good.
I guess that's totally fair. People are hard wired to pattern-match faces, and someone who deviates from the norm will attract attention.
I was more talking about judgement of people who did just to still look normal but better, similarly to the judgement of people who learn "social skills" like the TFA discusses.
That too is pretty obvious from the same perspective: Admitting you only care about someone’s genes is itself considered shallow, so people make up other justifications based on other, more accepted values.
