> Writing a compiler for a pure functional language would certainly need new material.

I mean, Haskell is also over 30 years old at this point.

Yes, but it's changed a lot in 30 years.

On top of sibbling comment, Simon Peyton Jones seminal paper is from 1987.

He has spent the last 30 years since publishing more papers on compiling functional languages.

Mostly related to adding new features to Haskell and GHC, not on compiling functional languages in general.

Now functional logic languages like Verse, that is definitely new material.

That's selling him very short. I would say most of his papers are applicable to functional programming in general and not just Haskell.

Only for those that understand functional programming as whatever Haskell does.

No, I think it is because most problems are too hard to solve. Think a simplified case: build a compiler for evaluating arithmetic expressions like "a*3+b" and make the generated code as efficient as possible. It is an NP-hard problem!