Wow am I glad I learned JavaScript in 2012/2013.
A few years later, I was most comfortable building web servers with Node/Express.
Once again, wow am I glad I learned RoR and then Elixir/Phoenix instead of halting my education and sticking with what I was most comfortable with back then.
It's been a huge productivity boost in multiple domains.
My personal developer stack is getting slightly dated as my main focus over the past few years has been onto dev/sysops, seeing tons of new exotic tech being used now and then.
I am really open on learning something new today if it can help me be more efficient in building my ideas in the future!
There is a local maxima around what you already know due to the cost of learning something else, but it's much shallower one than many, including my past self would have guessed.
With web there are a lot of transferable skills: http, DOM, chrome debugging, general problem solving etc. so there is that too. If I try nextjs and it does something odd I can still debug it.
I mean JavaScript pff... that's so last decade.
/s