Why does he want to hire them would be the first question I'd ask.
As a player, I'd be incredibly suspicious, assuming there is a damn good reason he doesn't want to hire, say, a couple dozen fighters and a team of archealogists or at least some experienced proffessional heroes instead of a team of noobs, especially if its supposedly valuable. Perhaps the object is dangerous and we're expendable? Perhaps its a trap? Maybe he just wants to keep things on the down low, and we should try to avoid being obvious about who we're working for? And most important, why is he entrusting us with this important mission.
Anyways, to clarify my last post:
There are two distinct types of roleplaying, really. There's character roleplaying, coming from the theater/literary tradition of unstructured roleplay, and then there is dungeon crawling, coming from the wargame tradition with a focus on stats and combat and winning, with everything else as "theme-setting" more than building a dynamic narrative. D&D was originally based on and is still very much a servant of the second tradition, and those who value the first tradition (or some of the other less popular traditions) more highly often suspect (often correctly) that those who've only experienced D&D have a very limited view of what roleplaying means.
There are a lot of other divergences in ways to roleplay and approach roleplaying as well, and if you've only done D&D you need to realize you've experienced only a very small slice of the pie, no matter how crazy your DMing has been. Not just setting wise, but mechanics wise. You might not realize just how much a systems mechanics can guide the way a game is played, and you might be unaware of the diversity of roleplaying experiences available to you (even WITHIN D&D!) if you haven't experienced a system that guides you naturally towards those sort of outcomes.
It's similar to the criticism that someone who's only ever read, say, a certain style of detective novel, doesn't really know what "good" writing is. They may have experienced good writing in several of their novels, but they really don't have any idea of the breadth of what it can do outside of its narrow genre. Of course, people argue that such critiques are worthless as well, but surely you can see where the opinion might come from.