DM fiat is the game, though.Right. But, as pointed out, boons etc exist in the books. So we have that in common. Trouble is they're locked behind DM fiat. As we don't all share the same DM...that's where the problem is. It may be a technicality, but it's a distinction that makes a difference, I think.
And to be honest, I don't see how Online Discussions can truly be productive if the entire game's arbiter is left out of the discussion entirely.
Sure, we can't agree on how a DM will behave, but the DM must exist and therefore must be considered.
If the problem is because of "Guy in the Gym-ism," would it not be productive to remind the community of how to help within individual cases rather than just not speak out?