Yes, that's an incredibly bold statement. Javascript today is probably the most popular language in the world (according to Github; other indices tell a different story), and that gives it the very same role that at once was fulfilled by Java or even PHP: it's probably the first language a newcomer will learn programming with, hence you'll find a lot of unskilled engineers as well as some experts.
So, saying that Javascript devs, just because they're interested in Elm, are "the cream of the crop"... sounds ludicrous.
Good for him. Let's compare the 2 languages in 20 years, and see how the language for the infantilized target audience is doing. I'm fairly certain Elm won't even be a footnote in history.
To be fair, many items in history got popular being ... err, for the infantile; some primarily because of it. But I don't think popularity is one of Elm's goals.
I use what I use because it works for me, and not because it's the fashionable trend; similarly, I think while Java has its place, I'll use Elm when it works for me. And not being dumbed down certainly serves some functions.
Whereas taking something old but reliable and throwing whiz-bang new footguns at it is how we got C++. Don't get me wrong, it's still one of my favourite languages, but damn if sometimes it isn't like an alligator with a bunch of broken glass glued to it.
(cringe)