I attended exactly because of those reasons. The problem is mostly that actually explaining a language (even from a high-level overview) well is a bit more involved than just explaining the syntax and the like.

For example I currently mostly work with Go, and if I would give a high-level presentation about Go I'd start with the "tour of Go" tutorial, but I'd also add some context to some things, explain where you need to be careful to avoid problems, and emphasize the usefulness of other things that may not be obvious at a glance. That kind of stuff. I think the presentation format is a great way for doing that.

A beginning JavaScript programmer might explain the "with" keyword, which would be a mistake. I have no idea if the presentation contained any mistakes like that.

I don't work much with JS, and I haven't looked much as TypeScript since, but I didn't really learn all that much more than what I already knew: "TypeScript is JavaScript with optional typing".

Was it useful for others? Maybe; I hope so. But for me personally I consider it a wasted hour in my life.