I agree with the point, but the argument -- that by arbitrarily ignoring features you come up with a simple core language -- can be applied to Haskell (and pret

I agree with the point, but the argument -- that by arbitrarily ignoring features you come up with a simple core language -- can be applied to Haskell (and pretty much any other language) as well. If you exclude typeclasses, extensions, and IO from Haskell, you get a very simple language. (I personally find the error messages easy to understand when avoiding those) Related: how GHC compiles Haskell code, including the "Core" language and lots of desugaring.