Sorry, this is really bad advice IMO.

"1year or more out there are entirly new stacks, new libraries, new versions, new ways of building things etc."

You think there are any dev teams which change their entire stack every year? As for new libraries, thats what documentation is for, nobody gets hired because they have a the newest & hottest libraries APIs memorized.

Being a good developer has very little to do with knowing all of the trendiest new tools. A sound understanding of software engineering practices and methodologies is far more important.