My experience has been exactly this. I've read many such complaints in the last 20 years of working, and in every single case the author has pigeonholed themselves into a long obsolete corner of the industry. There is a difference between 30 years of experience and 5 years repeated 6 times.
It is important to get onto the right team to have a long lived tech career. Your business domain should be big enough so you organically have to move with the rest of the industry. By 20+ years, you should be in a senior enough position to help lead the change.
I've never met a tech guru who was up to date and didn't retire or move on to other things on his/her own terms.
That wouldn't surprise me. Larger companies are often well advised to keep their production languages to a minimum. I mean, even Google when they first started out (straight out of grad school) wisely restricted the number of supported languages.
If you stay with the same company for a long time, I can easily imagine that you don't get a lot of exposure to new trends. I mean, C has been around for a while now and depending on the field of application can still be the go-to language.
Python/JVM/Ruby are the opposite: It's more about a diverse skillset, because most of the time you'll have to use Java AND Python, or Python AND Ruby.
I suspect there is a geographic mismatch. COBOL programmers probably can't be remote-only.