I think, and I'm just speaking for myself here, that the problem I have with the basic premise of a neutral DM is that it ignores the fact that D&D (and RPG's in general) are made up of a number of different games at different times. When the DM is creating an adventure, it's almost impossible to be actually neutral. Unless that adventure is 100% randomly generated, the DM will ALWAYS have a thumb on the scale. Has to. And, is advised to PUT a thumb on the scale during scenario creation - sure, randomly roll your treasure, but, if it is too much or too little, roll again goes the advice in the 1e DMG.
Sure, you can create a "living, breathing world", but, at the end of the day, you're still building a campaign so that "living, breathing world" is filled with adventure stuff for adventurers, which, unsurprisingly, will be based around the levels of the characters (the top level of the dungeon has the weakest monsters and monsters get stronger the deeper you go, in a low level adventure, the encounters will be spaced further apart to make sure that encounters don't bleed together, on and on and on).
During creation, there's no such thing as a Neutral DM. Doesn't exist. The DM is there to create stuff for the players to play in and that will obviously impact what is being created. You don't bomb Red Dragons in 1st level adventures. Killing PC's is easy. Challenging them just enough to make them worried, without killing PC's too often or to randomly? That's a skill.
Now, during play? That's where the Neutral Arbiter lives. You don't want the DM going too far in either direction (either for or against the PC's) because that's no fun for the people sitting at the table. Again, sure, I can smoke PC's pretty easily, regardless of system, just by leveraging my power and authority over the game as DM. It's really not that hard. Or, I can make encounters entirely cakewalks just by playing dumb and doing dumb things with the baddies. Oh, you want us all to group up tighter so that fireball gets all of us? Great, let's go.
But, I do think that the conversation has to recognize that there are different games going on here. The role of the DM during creation and the role of the DM during play are not necessarily the same, nor are they necessarily going to fall under the same categories.