That’s odd that this article has so little claps and no responses — it’s definitely what is going on for a while now. Some people (especially the ones who are comfortable with the status quo) are complaining that their skills are the important ones and they don’t want to learn those less-important ones like UI (I disagree strongly with that).
But I think the main reason for generalists is that you are able to speak the same language as other people in the team. So there are no gaps in communication and that leads to much better products.
If everyone knows a bit of UI, everyone can contribute, and then the person who is best at it can wrap it up and finalise. But at least everyone is on the same page all the time.