Finding a playgroup for Descent is indeed hard. First of all, the people need to be experienced board gamers, otherwise, there might be too many rules, too many mechanics to deal with. Secondly, they have to like the fantasy/RPG theme. Descent works much better in my opinion if you read the flavor text. But most importantly they have to be able to take a beating. Descent is not a video game like Diablo III where you are supposed to hack 'n slash your way to victory. The people your are playing with have to understand that. But at the same time, I think you have to play nicely. If you have the OL card combo that can break the game, you shouldn't play it if the heroes are having a hard time.
It makes Descent (campaign) a very inaccessible game, but very fun if the two parties know how to play it in a way that makes every quest genuinely exciting and suspenseful. Your fellow players don't have to mind being the losing team (or person) after a 6 hour game night.
I know what you mean. I only got my copy yesterday but even before I ordered it, I knew I was in a situation where almost all of my friends are of pretty mainstream tastes. They don't like fantasy, typically only watch films that are set in the modern day (or at least 20th century) and have no clearly fictional elements. The only board games any of them have played are things like Monopoly and Risk. It was the biggest factor holding me back from getting Descent earlier. I mean, you mention Diablo III yet even that is too "geeky" for most of my friends. They'll just play GTA and FIFA, stuff like that.
I think this is one of the biggest things holding board games back - at least ones that aren't highly randomised and (IMO) boring such as Monopoly and Risk. You can see how in videogames, online multiplayer has totally obliterated local multiplayer. People simply don't have all that many friends, if any, that share all the appropriate interests and have the free time to make local multiplayer games (board or video) that feasible. This is also perhaps why the co-op expansions for Descent are totally sold out everywhere (at least here in England) since it allows solo play, or just two people to play side by side rather than against each other which is more palatable for new players.
I don't 100% agree with you that Descent is all that complicated, although perhaps that's because I used to play Warhammer 40k (2E) back when I was about 14-16 so by contrast Descent is very accessible and user-friendly. The irony with Descent, and other FFG products, is that all the various cards and tokens make it very easy to manage and understand compared to stuff like 40k, yet it's the abundance of all those elements that make it look so complex and daunting to non-players.
I think it is rather strange that Monopoly and Risk are that popular. Gameplay isn't fun (for example, combat in Risk vs. Axis and Allies) and they drag on waaay too long. And it is a shame people play more online than local, they point of games is that you play them with your friends (or at least with strangers whom you get to like in the process)! And yeah, if you have a Warhammer background, Descent is fairly manageable. Not so when you only play Settlers of Catan, and the fantasy theme might also increase the threshold. Maybe introduce them to some simpler games first? Like Legends of Andor? Shut Up and Sit Down reviews games with the goal to make board gaming accessible to everyone and introduce new people to the hobby, especially their 'Opener' video's! And they have a great sense of humor IMO:)