> Second, even if they did erroneously make a claim about the feature's novelty, I think the theory type of people dismiss these sorts of languages too readily. Yes, somebody did it before. But it is usually very hard to bring these features into the mainstream or even adjacent to it.

It is, because people are unwilling to use them in existing languages. So it's extremely frustrating when what feels like the same people who've been trashing Haskell for ten years get all excited about how their new trendy language has this brilliant new feature... that is the same thing they were complaining about being pointless academic complication when Haskell did it.