Following reality in a fictional RPG world is futile. Any attempts to add "realistic" drawbacks/limits/rules,
(e.g. needing/changing special weapons/equip for specific area(underwater/volcano/forest/climbing)) which rely only on the "it looks more realistic" justification and not game balance should be thrown out: game balance issues should not be used to introduce realism too - it should be opaque stats which determine balance, external changes must not rely on realism. Player should not be hampered or limited by "realism" at any point: the game is not replica of some world(not an interactive movie).
It easy to set into the 'realism trap' with game design, which result in such things as limited stamina for running, item durability loss(inevitable repair) and health potions not healing instantly("healing the damage" slowly: this seems more 'balanced' but provides less utility to player).
These factors which increase realism without bothering/affecting gameplay in negative way are fine: its only where realism dictates its rules to gameplay mechanics.

Eye-Candy Realism vs Mechanics Realism:
Eye-Candy Realism is basically expensive graphics/sound assets to conceptually represent a "physically accurate" world.
Mechanics Realism is attempt to take real-world laws or rules and put them in game world.
Mechanics Realism:
While it seems things like gravity are necessary for realism, it creates an undue burden on game engine, as most objects don't need to use it(they are either stationary, flying or located on the ground) and objects that need it(jump scenes, thrown items, projectiles with weight) can calculates their trajectories at their own pace - universal gravity for everything would slow down everything.
Eye Candy realism:
Each object could have realistic shadows and lightning, but players don't play the game for the art and don't concentrate on small details like accurate refraction/shadows/shading.
Instead a screenshot system would create the best frame with most eye-candy(raytracing or best/photorealistic quality) and save it to disk, while the game itself would play with "acceptable" graphics.
A compromise is allowing better quality graphics where the viewpoint is static for N seconds(i.e. idle character) if player has enabled it in settings.