"Language agnosticism" is an ideal I have never been able to attain. Sure, I can hack together a solution on the first week of learning a language. But, am I able to write elegant, idiomatic, efficient code during the first few months? No way.
A language is not just the basic control flow operations, but includes package management, performance gotchas, correctness gotchas, standard library, library ecosystem, data representation, etc. Then there are details and edge cases that you just don't hit without months or years of hard work with a language.
My experience tells me to take choose a reasonably robust language, then stick to that language until you have an overwhelmingly compelling reason to switch.
0. Define what problem you are trying to solve, make sure you understand the domain.
1. Come up with a set of options by doing research, talking to people who have solved similar problems before, etc.
2. Rank them by some criteria (e.g. availability of libraries, documentation, raw performance, hireability, support, quality of tooling, etc).
3. Do some prototyping in your problem domain using the top 2-3 (more if you aren't confident in your ranking) and pick whichever you like best.
4. Always be willing to change your mind down the road. Avoid the sunk cost fallacy and try not to lock yourself in too much until you're confident in your choice.
Understand a lot of programming languages, become proficient in a few and use your understanding when trying to come up with solutions for your problems. At least play around in other technical stacks then what you normally use, so you get a broader understanding.
