That explanation of the rich young man is like the myth that there was a gate called the Eye of the Needle. It's a rationalization created by and for rich people. If the advice was only to the rich young man, it would not have been recorded. It was written down because it's for all Christians.

That there were good people who did not follow Jesus's advice is certainly true. But they followed John the Baptist's advice and gave half of their wealth. See Jesus and Zacchaeus.