Below are my thoughts after reading Ben Fritz's article in Variety regarding reviewers obsession with the game details and downplaying the game's overall "big picture.":
Video games are unique because they combine other classical forms of entertainment and allow the player to move through these mediums literally and figuratively through gameplay. Gameplay is the driving force because gameplay is what separates video games from other mediums such as television, paintings, books, etc. (Sorry for the Captain Obvious statements.)
Books can make us laugh. Movies too. So can T.V. Video games make us laugh as well, but that's just the tip of the iceberg. If our interactive medium, video games, has done its' job, we were made to laugh because we caused it to make us laugh. Our inputs resulted in an output that caused us to evoke a type of emotion. That's pretty powerful. Instead of passively watching a movie, we were in control and actually physically invested (albeit only with our hands and fingers mostly) into the outcome of our inputs. It took some effort to reach that emotional outburst.
The point I'm trying to make is that gameplay, controls, input/output feedback, AI...the combination of these systems unique only to video games need to, at the very least, collectively be equal in quality to the theme, the art style, the story, the writing, and whatever borrowed mediums are used in shaping the game's vision. They need to be equal because the combination of these systems enhance (or detract) from the game's artistic expression/goal. If anyone of these systems isn't up to par to current systems, the suspension of disbelief will be broken. Flow is broken. Many gamers have been conditioned to sort of recognize what is established quality of any video game system. If any system is out of whack, the artistic goal of the game could be quickly dismissed by the player.
I do agree that there are way too many great scores nowadays. I attribute that to sequelitis as well as "groupthink" as one journalist mentioned in one of her blog posts. At the same time, however, I believe mechanical problems and concerns should be at the forefront of the review as well as the game's "big picture" and the developer's attempt to push the medium into a more well rounded direction. Like you mentioned, there doesn't seem to be a good balance of this as big games don't get called out for obvious, obvious sub-par systems. For example, GTA is notorious for horrible combat systems, gun or melee, but yet inundated with 9s and 9.5s.
Video games are the art of electronic interacting and without the solid mechanical/gameplay/control foundation to drive the intuitive feel of the player, I believe the game's vision is already at a disadvantage of being realized.