I would have argued that being a neutral arbiter or referee as you say is a key component of making it fun for the players. Overcoming real challenges is more satisfying than having the DM fudge things so you always end up winning.
You cut out important bits in what you quoted that addresses exactly that.
I am fair and consistent in my rulings, and provide real tensions and fear of death without fudging so that rewards are well earned and they have epic stories
because that's what gives fun to my players. It also provides fun for me. Providing that real challenge to the
characters is one of the ways that I provide fun to the
players. If I was teaching young children to play, I would have different parameters, since that is what would be the most fun around that table. There is only one team - the people sitting around the table (which includes the DM). They all want to make that team win (everyone around the table have fun).
It is only by falsely conflating character success with player success that the misguided idea that a DM should be impartial has any traction. DMs fell for it as well, with the old adversarial DM idea. The DM should NEVER be impartial -
they should be actively working for more fun at the table for everyone (including themselves). By the flip side, the players should never be impartial either. They should also be actively working for more fun at the table for everyone (including themselves).
In a game with multiple sides, it provides fun to have a neutral arbiter to provide fairness. The idea that the players are a side, the DM is a neutral arbiter, then leaves who to oppose the players? (Note: not to oppose the characters.) No one. Without that, the idea of a neutral person makes no sense. I know it's been one of those ideas that's been around for ages, but it really needs to be reexamined instead of just accepted.
Just like players and characters are different, the challenges, setting and foes the DM sets up and controls in the world are separate from the DM themself. The DM and players are on the same side. The characters and the challenges are not. Or maybe, through clever play, they are.