Bedrockgames
I post in the voice of Christopher Walken
That is kind of an odd thing to say. The only truly 100% indespensible elements to the game of Dungeons & Dragons are dungeons and dragons. They are right there in the name. If you do not have them, then it can only be taken as an indication that someone has failed their Knowledge (Taxonomy) check.
But you could have several campaigns that have neither dungeons nor dragons, and still be playing D&D. I don't think these are an essential feature of the game. To use coca cola aggain as an example, it no longer contains spent coca leaf, but it is still coke.