As a programming languages researcher I disagree. HTML is not just a programming language (a declarative one), it literally has the word “language” in the name. The world of programming languages is much larger than general purpose languages.

Also, whether JavaScript is interesting is a matter of opinion. Given that for a long time it was the only web language, I’d say that makes it interesting. It’s also in my opinion a poorly designed language but that also makes it “interesting” because its behavior is sometimes hard to predict.