Yes. The time to put energy in is when there's truly a new paradigm at work. Not when it's just another version of something you've already seen a half-dozen times before.
Bootstrap? Cool. Maybe follow that up with 1 or 2 other grid systems. But if you start chasing every layout framework coming down the pike, you're wasting your time.
Same goes for imperative vs. functional programming. There's a big difference. You should know that.
I think where the problem arises is when there's some new cool version of the same thing. You probably already know how it plays out, so your rational response is to not bother. But if you don't have it on your resume, you're going to be doing some fast talking.
There's a difference between learning in order to execute and learning in order to impress. If you want to stay in coding, sadly, you gotta keep learning. And the things you learned all have to do with marketing yourself, not being a better programmer.
I think that's the part that sucks most about getting older as a coder -- watching the community walk away from solution delivery in order to intellectually amuse itself with 4 or 5 year fads, which usually involve a cool video and a ton of hidden complexity.