ADVANCED DUNGEONS & DRAGONS is first and foremost a game for the fun and enjoyment of those who seek to use imagination and creativity. This is not to say that where it does not interfere with the flow of the game that the highest degree of realism hasn't been attempted, but neither is a serious approach to play discouraged.
- DMG p. 9: "The Game: Approaches to Playing Dungeons & Dragons"
Now, in the interest of being as clear as possible, allow me to unpack the latter two clauses and clean up the double negatives. If we do so, we read this:
(1) The highest degree of realism has been attempted (so long as it does not interfere with the flow of the game).
Again, the double-negatives make the slightly hard to parse on first viewing. In fact, we do seek the highest degree of realism -- claims that D&D has "never been realistic in any way" are totally false. Purely abstract systems are not of interest to us. However, if a conflict arises, then what must take precedence? Definitely, the flow of the game. Both elegant gamesmanship and realistic modelling, working in synergy, are the zenith of game design; but if those goals come into conflict, then gamesmanship must clearly, (narrowly) win out.
(2) A serious approach to play is encouraged.
We can allow ourselves to be serious about our gaming. Claims that "you're thinking too hard about fantasy" can generally be ignored as meaningless. And at the same time, if some of our friends are most interested in the fantastical, phantasmagoric, and even comical elements of our gaming, then that should be seriously respected, as well.