As a young engineer , I constantly get the feeling that I'm falling behind and that I can't be maintaining any single project for way too long.
One reason I think I must learn new languages is that projects written using new languages will be new stuff that's written from scratch. There's nothing wrong per-se with say Java but the odds are that if you have Java experience you'll probably be stuck maintaining some decade old enterprise app.
The same can be said today for say RoR. However if you're applying as a Go or React.JS developer you get to work on a lot of new stuff whereby you get to learn a lot more by writing whole projects from scratch.
So in such a highly competitive market people can't be blamed for being so buzzword driven.
Maintenance experience is not at all valued in the industry and people who do maintenance are looked at as lesser beings. That's the reason we keep throwing things out and reinventing the wheel.
Everyone needs to create a me-too JS framework and put it on Github so they can get hired by claiming that they're some open source rockstar.
Personally I just keep running to stay in the same place and end up learning nothing in depth because I'm spread too thin.
At some point there is an operational advantage to having a consistent set of core technologies. If we make it so that the only way engineers can be successful is by constantly looking up answers on SO or elsewhere, then I think we've failed as an industry.