Office COM automation is what I did. I get what you mean, but in my experience, interfacing with native code is not always straightforward. Also there are odd cornercases where you need to fallback to p/invoke.

But More importantly, you can't change anything, you can only use it. So the FFI is nice and easy, but you could say the same about other languages. Or am I confusing things with Smalltalk images? Cl was somewhat before my time.