I guess as a tabletop RPG you can run some sort of hyperrealistic variant of D&D, but at its core it's got a few to many talking swords for that sort of thing.
Okay, let's try a different analogy. Let's say there was an urban fantasy where dragons attack present-day New York. If a character's 1993 Chevy Corvette breaks down because an issue with the carburetor, we wouldn't just say "it's not supposed to be realistic; dragons!" It would rightly be seen as an oversight by the author. Arms and Armor are a technology and D&D at least pretends that the (non-magical) versions of them are based on said technology.
This is how a lot of fiction operates though, it doesn't attempt to portray realism first. This is true in everything from western movies to rom coms. The story comes first, and the details have to be just believable enough to not stick out so much as to break immersion.
Although what breaks immersion varies. Someone who's at most shot a few cans or a deer won't perhaps question a bad guy being sent flying backwards from a revolver shot, a war veteran might see this as jarring and unrealistic.
But it has often represented itself as more than that.