You are reading in something I never said.
This is what you are reading in: "this does not mean sed is not a tool worth learning"
I never said, nor implied, that.
None of my prior responses have said whether sed is worth, or not worth, learning. My responses were focused only on your initial hypotheses that implied a large number know of it. My hypotheses is if you actually test your statement within your JS dev. groups, you'll find a shockingly low number of members who even know sed exists.
Now, as for my opinion of sed, it is a fine tool, and it is well work knowing how to use it (at the very least knowing how to use it for its most common usage, replacing strings with other strings). I myself reach for it quite often when I need to do something that it is good at doing.
And, yes, for you, it is well worth learning something about it. It is also well worth you learning something about many of the other CLI tools, such as head, tail, join, comm, seq, etc. There are a huge number of them, and they can often allow you to solve a problem without ever writing a single line of code (unless you consider a Unix pipeline to be 'code').