Why then would you want to claim an authority which to use is morally wrong?
That a DM could do something morally wrong is not a good thing, but you seem to want to defend the right they have to exercise just that authority.
Yep.
And then, in the highly unlikely event a DM ever does exercise that authority, I'll base my response on the specifics of the case at the time: I might agree, I might not agree, or I might not care.
That you would do so is rather beside the point that other people have done so.
And since they have, and it worked, then it logical to then put forth that a DM is not strictly neccessary to run the monsters. Because, sometimes, people let the Players run the monsters.
Asking people for individual answers to a question and then complaining when this individual's answer doesn't speak of situations not my own isn't cricket, old boy. Try again.
Why is saying the game belongs to the entire group a deal breaker for you?
Because the game, in the end, usually* belongs to the DM. She's put (and continues to put) the effort and prep in, she's done the legwork, she's not only driving the bus but is also its mechanic and - often - purchaser.
And if the game she wants to run isn't to anyone else's tastes (which, in a group of friends who already know each other, is rather unlikely), then she's out of luck.
* - I'll except pick-up games, one-offs, and some AL games here: pick-ups and one-offs because they tend to grow out of a group sitting around and deciding what to play for the night and who will DM; AL games because the DM has to answer to a higher authority, that being the AL organizers.
Considering we just proved that you can run DnD without a DM, something you flat out admitted was possible, then how can you turn around and say that "yes, you cannot run DnD without a DM"
I probably should have put the word 'worthwhile' in there somewhere.
So the players need to know every houserule, every public knowledge detail and all of that months before the game?
Not at all. Merely a few weeks before intended puck-drop, when I approach them individually with this material and invite them to play if they find the material interesting and-or agreeable.
No, that is when you start making things, but that isn't when the players are informed of them.
I guess if you do a whole bunch of pre-session zero talking, that is when these things might come up, but seeing "the dice hit the table" and realizing you probably have everyone roll their stats... a player might roll stats that inspires them to play a paladin during session 0. Being a paladin they would want to be part of a holy order.
Do you honestly restrict them to a specific and limited group of potential holy orders, with no input from them at all?
First off, yes: stats are rolled here, end of story.
If someone rolls stats that allow for a Paladin and wants to play one, I'll direct the player to the deities chart that shows which deities support Paladins (Paladins are as divine as Clerics and based out of temples, I've never done the separate Paladin-holy-order thing; and a non-divine Paladin would be a Cavalier instead) and the player can either pick a deity then - which would determine which culture the PC is of - or can wait until determining culture/background and then revisit the deities list and pick at that point.