I personally feel that game journalists should at least have an interest in game design, even if they don't want to make a game themselves. My path to wanting to be a games writer came after I sought to try and be a game designer, and when I wanted to be a game designer I learned to analyze video games in a much different way than I had before.
One of the things I see in journalism now are too many people that are simply gamers that can write well. So called journalists covering events without any real journalistic integrity and unable to remove their bias from a review, or to see what a game has to offer on the whole.
I recently played through Mushroom Men: Spore Wars, and while it wasn't a game I would have bought for $50 I certainly saw merit in the title. However, the review scores were absolutely painful to see. There were outlets scoring it a 2/5 when it had some excellent control, an amusing and creative style, clever boss fights and puzzles and massive environments. The only thing wrong with the game was the camera and the fact that it was five hours (and the fact that each death was followed by insta-respawn, but let's just argue we're going for accessibility here). Mushroom Men was scored as if it was a half-assed game when, in fact, it was a fun experience that a much wider array of players could enjoy than, say, Gears of War. The only difference is one is much more "hardcore".
Similar sentiments to the recent TMNT: Smash-Up game. It's a solid title and in particular caters well to the gamers that prefer no-items-final-destination in Smash Bros., but because it was lacking characters, power-ups and a lot of other content stuffed into Smash it was scored low instead of being considered all on its own. A good game was rated as if it were crap.
Then again, maybe this is just the difference between integrity and being a jack ass, though I still say it was through studying to be a designer that I gained a sense of "what kind of people might enjoy this game?".