I do a lot of sales now, and I've watched a lot of enterprise salespeople do their work.
As in any other human endeavor, some of them are phenomenal. I routinely sat in on one friend's sales meetings and calls. After being raised watching Gil, the hapless salesman from the Simpsons, this was like watching Billy Joel play the piano or Roger Federer play tennis. It was obvious he was a master craftsman. He was so expert at getting people to act in their own best interest, while making it look pleasant and effortless, it was - seriously - beautiful to watch.
Other salespeople... not so much. I've seen them too. They don't have the intellectual horsepower, they don't prepare, they... I mean, frankly there are a million reasons they're mediocre. Their mediocrity is overdetermined.
I think that's all the author meant by coin-operated salesperson or "script kiddie" salesperson: a mediocre one.