How much time does it take?
How do you judge the merits and demerits of the language?
Do people who know some PL theory judge it in a different way than those who don't? Like do they have a mathematical framework in mind and map the language docs to that framework to see what is bad or what is good?
For example:
Suppose I am to learn Python. I go to the official website and go to the docs page: https://docs.python.org/3/. I see a Tutorial section and a Language Reference section. I go through the tutorial. It is just a sneak peak. Then the Language reference?
Or do I read the Python source code?
P.S: For PL theory people what book/course do you recommend for that mental framework?
How good is the documentation? How well designed are the standard libraries? How good is the tooling?
Are there any great community libraries? Are these well documented? Is there a good place to find people online that are willing to help you solve problems?
Learning a new syntax is trivial and takes a couple hours to a couple days. Learning the ecosystem of libraries and tools to know the best way to solve problems takes years.
In general, I’ve found the best way to get started is to scratch an itch building something you want or need. Learning by doing is best.