Let me rephrase it then: fundamentally, JavaScript is sound. It's like a nice city with a couple of bad neighborhoods you can usually avoid. Other languages have much more pervasive bad features, and yet others are fundamentally unsound. JavaScript is fine.
Saying that "Javascript is fundamentally sound" is like saying "McDonalds serves fundamentally nutritious food". It's technically true, but ignores completely what people actually mean when they use the phrases like "fundamentally sound".
Let's take the empirical approach:
"Come, BrainFk isn't that bad: it's probably one of the most pleasant of the popular languages; it's just unpolished and has some stupid bits."
Nope, guess not.
Let me rephrase, "almost every language that is close to or has met its peak popularity"