If functional means "higher order functions", sure Lisp is quite functional. It's not ergonomic to compose functions in the way that Haskell is due to Lisp's f

If functional means "higher order functions", sure Lisp is quite functional. It's not ergonomic to compose functions in the way that Haskell is due to Lisp's forms essentially making every function able to accept a variable number of arguments. You end up with something like arnesi which provides these functions but it gets slow and verbose to write all those `funcall`'s everywhere. Or you have macros. Whereas in Haskell, partial application and composition are first-class in the design of the language. I really enjoyed programming in CL but I would say that it's one of those languages that let's you try functional programming but it's not the sweet spot for it.