This is good advice, but only if you are a junior developer with less than 2-3 years of experience.
If you want to advance professionally, you have to not care about tools, frameworks, languages, etc.
I think you're on the right path, you just have to force yourself to keep learning new languages, don't stick your head in the sand.
When you have 15 years of experience in programming, you are able to introduce new languages to yourself and to the company with no problems, identify idiomatic ways of using them, and teaching your collegues about it.
In the end, you'll notice that it's not something special. A new language takes about 2 weeks to master, and 2 more weeks to learn its idioms, afterwards continuous "lifelong" learning but in small steps about its ecosystem.
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