One difference between those friendships back then and then today is that with Romeo and Juliet's relationship, it was love at first sight where they fell in love with each other in a matter of minutes and that they already want to be together forever while today, it's more complex than that. Usually, people at first are friends that they get to know each other over time while their relationship grows over time. Then at some point, they would have feelings for each other and that they'd be in love with each other while after some more time they would get married and so on. In other words, while Romeo and Juliet fell in love in only a few minutes, nowadays relationships take time to grow. And that you can't fall in love with somebody that you barely know.
Hope this helped!