I don't think that 'first impressions being important' means that 'first impressions are the only factor in whether you like someone'.
Like, power to you all, you met people and changed your opinions on them. However, think of all the people who you did get an impression from and never had any further dealings with. That special someone who you wish you had gotten to talk to, or that weird person that you tried to avoid eye contact with.
Meh, whatever, people are really logical and rational. They can rationally think about what makes them like other people 🙂