Snap judgements exist, but IMO most are non-committal. You'll notice people who are very attractive or very unattractive, but most people you simply won't immediately react to sexually (well, except when you're 15).
Of all the women I've dated, only 1 said she noticed me (either way) before first developing a reasonably close friendship.
For the big middle, personality has a huge effect on perception. See e.g. https://psychcentral.com/news/2007/11/30/personality-influen...
> why won't you care about your physical appearance? Why leave something that important on the table?
Well, certainly don't be a slob. And not just because of dating! Dressing poorly and appearing unkept effects other parts of life too (e.g. career). Also, exercise is important for all sorts of reasons aside from attractiveness.
But other than being generally healthy and well-kept, I don't focus on my appearance because grooming is boring. Why spend your time grooming beyond a level of general acceptability when you could learn to play an instrument, learn a new language, read a book, or go for a hike?
If all you focus on is appearances, don't be surprised when the only people who find you even remotely interesting are other people who focus a lot on appearances.
