Spent time training with Joe Lewis years ago and even have a photo in my office with the two of us after a seminar. I learned the most important thing from him was that although I was damn good I wasn't world class.
To the "MMA would kill these guys" folks you are forgetting a few bits of info. Most of the traditional Karatekia from back in the day didn't just do kickboxing but rather were trained in all aspects of karate including ground fighting and stand up. At the time there wasn't any way of competing other than judo, point karate (my specialty)
https://www.youtube.com/watch?v=9NICLQaT9u8 ,or kick boxing.
A well rounded karate fighter doesn't care if you're standing, on the ground, have a knife or whatever. Cause in our eyes we're already dead and have nothing to loose unlike the attacker .