This is true, but there are a few caveats.
The one that I've been running up against most recently is that a lot of this new-fangled stuff does not really have a strong value proposition, and I personally do not want to waste time on it.
This has become especially true since "cloud" hit critical mass. Junk seems to get generated 20 times faster than it used to and see much wider adoption. GitHub profiles are now status symbols and everyone feels a need to have a bundle of their own showpieces to display.
A lot of the fads are totally perplexing, from the perspective of an engineer who is more interested in building a robust system than padding his resume. JavaScript on the backend (or, even more horrifying, the desktop)? Single-page app frameworks like Angular for everything, including very simple pages? Why?
Yet, it's hard to find a web-oriented position that isn't asking for a background with some SPA and some Node.js. Maybe it's a fad, but it's still going to impact your job prospects.
The takeaway: stay on top of fads and new tech, even if you resent it and think it's really dumb.
I had the same experience with Rails; I hated so much about it and put off getting serious experience with it for 4 years or so. Turns out I still hate it after years of usage, but it was much easier to find work, both as an employee and a consultant, when I had significant experience in the fad.
Didn't matter that I was learning all kinds of new tech that I thought was interesting. As much as one may hate it, it's usually best to bite the bullet and ride the market's waves.
The most frustrating one today is Kubernetes and Docker. Ansible was so beautiful. I hate Docker with a seething passion (not necessarily other container systems), and I see Kubernetes as a very rough toolkit for people who have Google-scale problems that no one should be trying to make for themselves.
Other caveats:
* sometimes techs DO go extinct. Though COBOL is not quite extinct yet, I've known COBOL coders who have gone years unemployed (that doesn't happen to anyone who knows a language/stack still in wide circulation). A small niche has pros and cons, and one of the cons is that the supply:demand ratio is fickle, and may not always be in your favor.
* It is very rare that your technical qualifications will be so unique that they will take precedence over your personal and political qualifications. This is something most developers try to dance around, but the fact is that tech is ultimately run by people, and they want to be comfortable more than they care about that loop's runtime. If you're looking for something that will confer huge career benefits, the odds are that improving your people skills will be more valuable than improving your technical skills. This is almost universally true. It's especially true if you think it's not.