I can't disagree with you because that's an issue of semantics. I would define "popularity" as the number of people using the language, regardless of skill level.

By that definition, I'd guess that Python is near the top due to its recent dominance in data science, but Stack Overflow isn't proving or disproving the idea either way.

Using my definition (and likely yours), JavaScript is certainly the most popular. But it's hard to discount the many huge organizations using Java and C#. Their beginners might not be using Stack Overflow as heavily because they have in-house mentorship.