I am a great fan of Haskell.

But the tooling and libraries of the JVM is a significant real-world practical benefit. Scala can get away with a lot of nasties for that. (In fairness Scala is very well designed, nastiness is normally all to do with Java compatibility)

Plus it allows Java programmers to start writing code almost immediately.

And yet the whole first part of his talk was problems with scala that are not problems in haskell. And many of those problems exist precisely because of java compatibility, which he acknowledges and says is not a good enough reason to do things poorly. By his own measure it seems like he should be using haskell.

I'm curious, what languages do you consider impractical?

Assuming practical is some kind of bar for "I'd use this at a company where I'd be deploying the project into some kind of online production" - there are a number of experimental/research languages that are better for offline research/analysis and don't have the ecosystem Haskell has.

I'm not going to mention them by name because if you don't know of them, then it doesn't matter and I don't want to slur them.