Most of those sacred cows - levels, hit points, classes, etc. - are what makes D&D, D&D. Take them away, and it's no longer D&D. There are plenty of games that don't use any of these sacred cows. Why not play them? I'm sure many would say it's because they can't get players for games other than D&D. Well, sorry to sound cold, but too bad. The game shouldn't be radically altered to please those who don't like D&D's core assumptions and mechanics, because I don't think they make up anything like the majority of D&D's current players.