Tony Vargas
Legend
So only important to the degree that game balance is prioritized as a design goal. Oberoni may have been terribly relevant to 3.5 when it was dreamed up, but less so to 2e or 4e - and not at all to 5e. The 5e DM isn't just allowed to change the rules, he's expected to overrule them consistently. Complaining about Oberoni in your 5e D&D is like complaining about macaroni in your Kraft Mac & Cheese. It's a foundation, not a fallacy.The reason for this is obvious - it's bad for game balance
The idea of the Oberoni fallacy is that you can't defend the quality of a rule by pointing out that you can fix it. Nothing much to do with taking the DM out of the equation - nor is refraining from pushing game-(re)-design work on the DM fundamental to D&D being 'really D&D' (other in the nostalgic sense of it being like D&D when it was at it's most primitive).The problem with the Oberoni Fallacy is that it assumes the ideal is to take the DM out of the equation and make a game that can run irregardless of good or bad DM adjudications.
5e's fundamental underlying principle is that, when you try to do this you end up taking away the quality that makes D&D most appealing.
5e tries to appeal to as broad a set of current and past D&D fans it possibly can, that requires a lot of flexibility, and leaving large swaths of play open to (or even in need of) DM rulings is a big part of delivering that. It's not that you can't have a clear/consistent/expansive/complete system that handles a broad range of styles, either, but the alternative of 'Empowering' the DM has the virtue of evoking the way we ran games back in the day, when the game "needed fixing."
Today, it's not that 5e is broken, but that it's open.
Bottom line, Oberoni doesn't apply to 5e.
It doesn't matter how good a system is, you can always toss it and go free form if you want to. No one can stop you. With an at least basically functional system, you just also have the option of playing 'RAW.'let go of the strict interpretations of the rules and strict usages of powers and positions and just ran with the free-form of roleplaying. That's something you can only do with when "Rule 0" is made the centerpiece of the game.