Oh, I have nothing against new ideas in programming languages, and I think the more "researchy" programming languages are invaluable to the community in the insights they provide on what works and what doesn't. I was simply responding to the befuddlement that the industry prefers languages that adapt ideas slowly, rather than those that are cutting-edge.
The most important innovation in the Hindley-Milner type system was parametric polymorphism, since that is the thing that enables you to build more powerful abstractions. Since the release of Java 1.5 and C# 2.0 that is now fully mainstream, but it took more than 25 years.