That's not a great lesson if taken absolutely. Other people can give valuable feedback to social interactions. You should be aware of what people think, and be able to examine it, but not be ruled by it.
unless you live alone in a cave, what other people think of you is important. it is exceedingly difficult to succeed in the modern world without cooperation, and people will not help you out as much or at all if they don't like you. this means you really do need to care what others think.
that said, it is common to conflate this sense of "caring" with the deep seated need for external validation that many humans have. most people enjoy being appreciated by their community, and this is fine, but I think it is very important not to be overly dependent on this. ideally, one's self worth would come primarily from within.
* https://waitbutwhy.com/2014/06/taming-mammoth-let-peoples-op...
I used to care very much about not caring what others thought of me. It didn't work out terribly well for me — neither professionally nor socially (nor, to be honest, spiritually). Eventually I started to care about others, and I've found that my professional & social lives have improved immensely.
Man is a social animal; he lives in a society. Not to learn how to navigate it is to doom oneself to spending a lot of time wandering in a maze.