Hm, I'm not so sure this would even have worked on a tv series -- you can make a two hour movie dark and violent throughout, but 22 episodes? You need to lighten up occasionally, have a little humour, a little love, or else even the tragedy loses its force of impact after a while. Look at AtS S5, there was literally nowhere to go in the end. It reminds me of something Trent Reznor said, I think it was about producing Marilyn Manson's Antichrist superstar, that (I paraphrase) you can't just put one hard & brutal track after another because people will get tired after a while, it's much more effective to alternate louder and more quiet tracks.

Then again, I've always liked JW's story-telling and characterisations despite minor grievances, so perhaps he'd have been able to pull off an even darker and harder Firefly and made me like it. Although it's not as if Firefly in its current form is all hearts and flowers and baby bunnies, it's plenty depressing in its worldview, but it also has a certain something to balance that