The question is if you are a good writer, you are probably occupied writing books and trying to get a career going instead of wasting time with video games. If you were good and you know you were good, you would seriously work on an industry that have huge problems in keeping talent in it and just be another guy on a 800 people team that is completely outside of your ability of influence? Without mentioning that most gamers aren't exactly well read people so shitty writers get a pass and don't need to improve to keep a job, just look to David Gayder.
All of this sorta stands, and you can add to that the fact that the institutions which can give potential writers an education to go with their talent ('cause art is part talent, part craft) keep them sort of not interacting with guys who end up making video games, who are, well people who do applied math for a living. You can enroll in a humanities university and spend your entire life never having anything to do with people who do math (for a given meaning of "anything to do" and "people who do math"). But still, the "pros are busy doing other stuff" isn't true - text writing jobs are significantly less well payed and there are tons of unemployed but well read humanities graduates out there, far more than programers or even visual artists. And there is way too much competition for the consumer money in the book writing bussiness. A good writer who could become a staple of a video game franchise would be mad to decline an offer.
And the "gamers aren't exactly well read" is rather true, stuff is being judged an praised for being better than the competition, while the competition is lousy. An added problem is that there are well read gamers out there in terms of having read a lot of books or seen a lot of movies, but most of that stuff is derivative genre literature. The problem here isn't that there something wrong with genre literature per se (I've read and grew up on it, too), but the reason IT works is that it simplifies structural stuff which works exactly the same in more high-minded literature. But the consumer doesn't really know. It's kind of like if you had amateur coders copy pasting bits of code they like without fully understanding the syntax and the calls and deffinitions, except the you can "run" the end result no matter how much of a mess it is.
Also somebody who's a good writer for passive narratives like novels or comic books might not be a good writer for videogames. In fact those situations here where you are forced into a certain point of view or end up in a situation that conflicts with the gameplay is a consequence of that.
Some of them yes, and this is true even for some of what you call passive narratives - writing for comic books, writing for the theater, or writing for the movies, or writing books/stories are very different things. Heck, even short stories and novels can be as different as rock songs and orchestra music. But a decent writer (not a "brilliant individual genius", but simply a properly educated professional) can see how it's different, adjust to it and account for it. It's not impossible.
Yeah, the problem is that it is especially difficult to write good stories for videogames. Try to come up with a "serious" reason for our hero(es) to kill an army of enemies and/or solve a ton of arbitrary puzzles that doesn't sound fucking stupid if you read it out loud. At best you'll get a silly action movie plot.
As long as you have players sitting down to solve a ton of arbitrary puzzles and the mechanics appease their expectations, you can make the reasons make sense within the context of the game. Set the right tone in the beginning and don't clash with them without proper buildup/forethought/execution, hit the right notes at the right times, and you can get a non-silly action move plot, or a silly action movie plot which takes you along for the ride. Or you could get a decent film-noir plot - they're romantic enough to rely on style and feeling more than brains, but you have to know how those work. Something as simple as making Monica older by having a different portrait for her, and having her be less whimsical in the short time we get to see her would've made the whole game make a lot more "sense", or rather prompt your brain to interfere a lot less. A ton of people who mourn the loss of a decent godfather figure would have an actual godfather figure to mourn, while you could then use your team to gradualy reveal to you that this person was also a person who they personally had reasons to work for thus humanizing her and making her death mean something on both a social and individual level - without immersion breaking saccharine.
I think you could actually mod that into the game in a matter of an afternoon, with the existing dialogue trees, and possibly end up with less text than there currently is. I might be wrong, but the chance is rather fair. Video game writing doesn't have to be thought provoking, but it does require proper thought going into it while it's being made.
Say, is there a way to access the dialogues in an easily editable format? I'd show an example of what I mean, this is kinda like me bashing stuff without trying to contribute, and I kinda know I'm able to...