Go ahead and rate me autistic but how this legend is skewed in popular culture really annoys me.
Ovids version of the tale, which is the only version anyone has cared about since pax romana, isn't about some self absorbed dude who falls in love with himself.
Its about a giga chad who has women falling over themselves to marry him every where he goes. But Narcissus is a volcel who would rather prance through the forest and do nymph stuff than mess around with pussy. One day he hears a really beautfiul voice in a bush. He becomes spellbound but when the source of the voice, echo, steps into the light and he sees her face he has second thoughts and goes on his way. Echo is so pissed off by this that she prays for a curse to befall Narcissus - the first person he falls in love with will be incapable of loving him back. And so he sees his own reflection while getting a drink and falls in love so hard that he cant stop staring at himself until he either dies or commits sodoku.
Sounds simple? Well there is a bit more to it. When Narcissus was born his mother took him to a blind seer (who was a woman for 7 years because of a curse lmao). She asked this prophet if her son would live a long time and he replied "if your son never knows himself he will live to old age". So who exactly could fall in love with their own reflection? Someone who was intentionally kept from discovering himself, stuck in basically a state of perpetually toddlerhood by his mother since going through those normal youthful rights of passage would have lead to him figuring out who he was, and then like the seerer implied he wouldn't live long.
So arrested was his development that he didn't even realize it was himself staring back at him in the pool. And this is also why he turned down all those women even the super hot princesses with tons of gold. You can't fall in love with someone else unless you know a bit about yourself, what you want and what you are looking for and who really compliments you.
It has nothing to do with someone who was full of themselves, its someone who didnt know a thing about himself.