[jollybean]

This doesn't answer the question.

More specifically, it's probably not useful advice.

I'm a generalist in a few languages, and I'm painfully aware of my lack of 'depth' of insight into the languages I use when I'm not 'knees deep'.

For some niche languages, you can't just 'read a book' and 'check stack exchange'.

I think we should all be 'multilingual' but it really helps to have depth of expertise.