I think that the writers on Lost really took so much license and had so much liberty; before that, it had been a really specific formula for what a drama — especially a primetime drama — could look and feel like.
I think it and a few other shows around that time what, as a viewer, I consider to be the platinum age of television.
To have that massive diverse cast and truly unexpected events, and have an episodic side and then a really serialized side for the true-blue fans as well.
I think it was shockingly character-driven, but still exciting.