I do not 100% agree with this. In a full out RPG, sure, that would be a fail, but not everyone wants to make a character for a game, sometimes they just want to control one. To me, it seems part of the fun of Descent here is discovering the characters personalities as they go on their adventures. A mixture of game and story.
That said, I think it boils down to what @Benkyo said above: the game is boring (per Quinns, as I have not played it). While the heroes get abilities and items and some of the game mechanisms sound pretty cool, if just running up and doing a double attack is the best use of your time, the designers failed at making an engaging game, even if the characters and story are.