I am less experienced than OP, but I got the impression the philosophical difference is that with Lisp, you are trying to abstract things with a simple language and AST code generation (macros) whereas in GHC Haskell you are trying to abstract things with a very in depth language, heavily based on mathematical ideas (see all those language extensions!).
Yes. Though in theory you could use Haskell with a Lisp-like syntax just fine.
Many of the language extensions are sugar over a simpler (implied) core of the language. Some are purely syntactic, like NumericUnderscores. Some others like GADTs are semantic, but still mostly explained in terms of mapping to this simpler language.
