More seriously, there are lots of types of realism. I don't care about realistic, historically accurate armor, for example. Or economics. ...But I roll my eyes at "logic puzzle" traps in dungeons. Why would a mighty wizard protect his sanctum with a lock that can be figured out?
Because
he can figure it out. It's not a test for the intruder (actually, it is, because the PC is the effing protagonist and the logic puzzle is a challenge he's meant to overcome), it's ("realistically") a mnemonic for the wizard.
Of course, some of the logic-puzzle traps/locks really are tests - whoever trapped or locked the place up actually did want certain persons or even just sorts of persons to get in, someday. Keys can be stolen, passwords forgotten, secret mechanisms discovered - but a test of character will (literally) separate the good from the bad.
But there is a kind of "realism" that brings a story to life. That I agree with. What kind of realism is necessary just varies from player to player.
The above reason for the 'logic puzzle' is very fantasy, black/white morality, and, yes, very unrealistic in the sense that morality isn't really like that, but it's not lacking in logic or precedent in genre. In that sense it's the kind of 'realism' (verisimilitude, genre fidelity, whatever) that brings a story to life.
but I think that realism is an odd appeal thing to appeal to a conversation fundamentally about game pacing.
Realism is a holdover from the hobby's wargame origins, when historical accuracy was highly-prized. IMHO, it's part of the fuzzy line between game and simulation. Games are often /called/ simulations (Flight Simulator was a popular video game), simulations are often called games (military exercises are "War Games"). But there's an important line between game and simulation: games prioritize fun, simulations prioritize accuracy.
"Realism," as we tend to use it (or more broadly,* "Simluationism" as da Forge formalilzed it), is an appeal to trade away some of the fun of a game in return for gaining some of the accuracy of a simulation.
* I'll say that Realism is narrower than Simulationism, because realism is rooted in accuracy as measured against reality, while simluationism is purer in it's pursuit of the sacrifices that theoretically must be made to achieve realism, /for the sake of the sacrifice, itself/, even, indeed, especially, when there's no reality to measure accuracy against.