This is precisely a recipe, analogous to the (in)famous la pièce bien faite of theater, where nothing that doesn't contribute to the main plot is allowed to exist in the play. This kind of thing can be fun, but it's not the only way to make a fun game, or avoid monotony.
For example, several of Jeff Lait's games, "Smart Kobolds", and "Vicious Orcs" come to mind, have a narrative and a message, and everything in the game is focused on the message, with little to no extraneous elements.
Similarly a game may focus on "the roguelike experience" and ruthlessly trim extraneous elements in order to provide just that experience.
These are a great example of this kind of game, but this isn't the only kind of game I want to play or write.
In the other extreme you have the sandbox, it's messy, there are no directions, there may not be a goal per se, but it's a fun environment to *play* in. Minecraft and DF are exemplars of this style of game, there's no narrative at all, but they can be massively enjoyable and present emergent situations you'd never encounter with a more tightly-controlled game.
Somewhere in the middle you have 'bands, many roguelikes, Fallout, GTA, and Elder Scrolls, where there is a backbone of story, plot, etc, but there are a multitude of paths you can follow along the way, scripted or emergent.
Regarding extraneous elements, rather than excising them from the game entirely, it may be sufficient to enable the player to manage them effectively, ranging from simply greying out items that the player can't use, to incorporating mechanics that render all items potentially useful (such as Dungeonmans' museum, or Crawl's sacrifice mechanic). Similarly with enemies that aren't a challenge, a mechanic that allows the player to eliminate or ignore them may be sufficient. Perhaps enemies that you massively outclass simply run from you in terror and fade into the background.
