You will find intelligent people everywhere you look. Obviously not all people are intelligent, but intelligent people do all kinds of things that you might not expect. Working behind the counter is not even a good example of a place where I’d be surprised to find intelligent people.
If the concern about the behind the counter guy is actually something else, such as not making enough money for you or not having enough prestige, or maybe you worry that he lacks ambition and about the problems that come from that – then say so. By talking about your concern instead of beating around the bush you’ll have a better chance of assessing the situation to see if your worries are justified or not.