Also, Wes Cravens career arc is hardly unique. Look at other dudes who started in the same way as him around the same time, like John Carpenter and Tobe Hooper. There was a sort of magic window in the seventies in America, during the real hey-day of new, gritty, gorey horror films, where you could really make something original and shocking for a very small amount of money, and a lot of dudes launched careers off it that bottomed out when they ran out of ideas or, more accurately, the industry ran away from them (Tobe Hooper never really had a career but I was racking my brains). A kind of similiar thing has happened with Romero as well actually; the more money and technology these dudes get their hands on, and, in fact, the older they get, the worse the stuff they churn out becomes. Maybe the problem is, these guys only really made their films so gritty and atmospheric and realistic back in the old days because that was all they could afford to do, and the cheesy high concept shit they rack out now is exactly what they would have done back then, given budgets and technology.
Also, from a film-making perspective, I don't think any of them are really that good at working with actors.