What do you think is best? Know a lot of languages ( polyglot developer) or be good at just one.

Both?

That said I definitely couldn't get by in my current job with only 1 language, I use python and c++ daily

This a newbie

@devJoe base on what you assume that ?

Maybe is not objective, but I do think is healthy to know more than one. Basically everything is the same in terms of logic, and if you are a good developer will be easy to pick up a new language once you get the basics, will be easy too to get a new job if you see more opportunities in other lenguages. If you concentrate in only one, and become an asshole in the process presuming your choice is better... That's a different story.

I've been developing mostly in C# for years. Learned Swift last year an I now see so many new solutions to problems in C#.