Itamar hits the nail on the head:

If you think of yourself as a Python programmer, if you identify yourself as an Emacs user, if you know you’re better than those vim-loving Ruby programmers: you’re doing yourself a disservice. You’re a worse programmer for it, and you’re harming your career.

I’ve been preaching the gospel of generalization for many years. This industry moves fast. Today’s new hotness is tomorrow’s old and busted. Learn specific skills, yes. But always keep yourself above the fray. I am not a Rails Developer. I am not an Elixir Guy. Heck, I don’t even consider myself a web developer. I solve problems; sometimes by writing software.

Back to Itamar:

The technologies you use, the tools you build with, are just that: tools. Learn to use them, and learn to use them well. But always remember that those tools are there to serve you, you are not there to serve your tools.