I'm a Common Lisp user, and I would like to refine your claim. I don't think that many true "language features", like borrow checking and a static type system,

I'm a Common Lisp user, and I would like to refine your claim. I don't think that many true "language features", like borrow checking and a static type system, can be implemented in a Lisp (without writing an entirely new language on top - Lisps are generally Turing complete, so you can always write an interpreter for another language on top, but I would claim that at that point you're not "extending your Lisp" so much as making a new one). Instead, what Lisps seem to excel at is allowing you to implement syntactic sugar. For instance, you can easily write CL macros that give you JSON/hashtable literal syntax, list comprehensions (pretend LOOP didn't exist), foo.bar to access struct elements, and infix notation - those things that people think of as being "part of the language" but don't give you any new capabilities (e.g. closures, a MOP, multiple-value returns, conditions).