That could be more to do with the quality of stories posted on Medium that the fact that internet technology has rewired our brains. Many people still read books, both fiction and non fiction, in print or some kind of e-readers, for pleasure. Doing so requires long periods of cencentration. Yet the same people are also browse the wen, following links in a desultory way, hopping from page to page rather aimlessly.
It may be a little early to say the internet has rewired our brains, we have always had the ability to switch from intense concentration to ‘butterfly mind’ mode depending on the situation.