If you are a bit experienced and/or educated, you can learn most languages fairly quickly. I'm fairly confident that most programmers will become reasonably productive with using a new language in under a month.
The issue is however that many of us don't want to be just "reasonably productive". We are nerds who really love what we do and take pride in our craft. So we want to dive deeper and deeper, reach competency and expertise and increase the fun we have continuously.
This part of continuous learning and refinement is rewarding but also really hard. A particular language can get in the way of that or help us to become better in some dimension of expertise. There is a mindset behind a language that might fit ours like a glove, it just flows more naturally.
But this emotional investment can sometimes hinder us in the long run, when we invest so much time and effort into something we don't like to hear that our choice was arbitrary or even bad in some way or another.
The antidote do that is to keep learning new languages and technologies at a reasonable pace. Suddenly the emotional attachment fades.