"As for why lisp has been left behind in favor of other languages? Well, it's pretty much the same reason as why few people in America wear bowler hats these days, they're out of fashion."

But wait, I'm not understanding what you're trying to say. Bowler hats are a fashion, yes. But if I do wear a bowler hat, other than getting ridiculed, there is no effect on my life. I'm not suddenly three times smarter or more effective at work. If bowler hats made you three times smarter, even if they were out of fashion, I'm sure plenty of people would wear them. If LISP doesn't make me three times as efficient as $LANGUAGE, then, yes, it's merely a matter of fashion that it is not more popular -- but maybe it's also no big deal. Is that the point you were trying to make? Because if it isn't, blaming "fashion" is not advancing your case.