I cannot understand why a game is seen as "dumbed down" if there is no main hero and party leader. The "hero" and "exceptional sole saviour guy" subject is such a one-sided, boring and overstretched thing that I would be glad for a game without it.
I think you misunderstood concept.
Main character do not have to be a "hero".
It's just a sticker for a character that is at the heart of the story and makes all the crucial decisions. You do not have to be the chosen one, the secret son of the King or man with amnesia.
Try to compare the books with games.
Have you ever tried to read the novel without the main character? It's nothing great, practically just a chronicle. The same problem is with RPGs that do not have the main character.
Players want create character with whom they can identify. They want to feel that they are at the heart of the story and that they are the ones who make the decision. This is the very foundation of RPG games.
As I wrote earlier, there were a couple of attempts to create an RPG without a main character. Some of these games were very solid tactical combat games, but none of them were really successful because none of them had a good story. It is practically impossible to make a good story without main character.
BUT
It's MORE easier and cheaper to do the game without the main character. That's why a lot of people think that these games are "dumbed down".