[acdha]

I wouldn't pick on the COBOL programmers too much – they've had a half a century of decent jobs, after all.

The lesson I'd draw from that is that you want to avoid siloing yourself. Most of those COBOL developers worked on the same kind of systems, often in the same place, for long periods of time. That kind of deep specialization is useful but also dangerous to you in direct relation to where that larger field is going.

In the web space, this is complicated by the somewhat unusual browser environment: in 5 years, you will always be glad that you spent time understanding the DOM, ES2016 and later, modern CSS, how to debug in every browser, etc. because ultimately everything is built on top of them.

You may or may not benefit from having spent time learning the framework of the day and that will be in direct relation to how much of that time was spent understanding broader concepts and styles versus dealing with idiosyncrasies and technical debt in the code-base. That's especially true for things like build tools which are easily replaced without visible changes to a project – they're useful and to be appreciated, but they're more overhead than part of your value as a developer.

[jajern]

There are still COBOL jobs too. Where I'm at Fortran is still pretty popular. Hell, I just wrote an internal app to communicate with a Vax!