Yes, this story is dated. It is wonderful, and still worth reading, but it is definitely dated. The restlessness of the young narrator is, I'd argue, universal. Sammy's impulsive nature, his desire to have meaning in his life, even his need to take a stand/show off, are all universal. Even the power fantasy of the story is universal; who hasn't wanted to time a line as perfectly as Sammy tries to do when he says, "The girls, and who'd blame them, are in a hurry to get out, so I say "I quit" to Lengel quick enough for them to hear, hoping they'll stop and watch me, their unsuspected hero."
However, Sammy's attitude toward women is dated, as are many of the social mores that the store manager feels so certain about.