While I'm certainly stronger in one language I'd say it's quite normal to use at least 3 programming languages daily. As a Unix guy it's even more. If I just want to write a Python hello world I need to know some Python, some Bash, some Vimscript, some Terminal I/O. Many of my projects also have Makefiles, additional bash scripts (which includes SED and AWK besides Bash). Interaction with databases, APIs, JSON or XML or INI configs, HTML, etc is also common. And let's not forget that most systems that have grown over the years have a few DSLs to interact with their tools.

So before I finish my first coffee I've probably used 6 languages already on a typical work day. I think most coders in my company are fluent in at least 10 programming (&related) languages. And while our software development team is certainly better than my last gig I still hope it's not the top of what software dev teams can be.

And your most prevalent point is that company enforces some language usage. It's often not the same if you switch. So if you have more than 5 years you probably can increase the typical programming language fluency about 50%.

Also your example about switching stacks. Your first stack had .Net, C#, SQL, JS and JQuery. Now you at least sometimes also use Java, and whatever Bootstrap/Angular require.