He's talking about the first JS specification which was done in 2 weeks IIRC. I've seen such comments several times which completely discard all the effort made to improve JS until now.

The first version of the language, upon which all other versions have been based, was done in 2 weeks. There are fundamental shortcomings in JS that exist to this day because of that, and because the web has to remain backwards compatibility. So, despite all the improvements over the year, JS is still poor in some areas, particularly when you're talking about porting applications to JS. It was never designed for that.

He's talking about Javascript itself. The language has a ton of short-comings, hence the rise of languages that transpile to JS. I agree with the previous sentiment, we should replace JS with something better. JS is a nightmare.