It is why I find a predefined voiced protagonist incredibly limiting - in terms of RP.
I see people saying that, but I don't feel that way at all. Quite the contrary in fact. When I play a pre-defined character I feel like I am playing it and reacting how I would if I were this person with their history and experiences, but I think to any extent it would be like that anyway even if you created your own character.
It doesn't bother me that I didn't set their history and in fact it makes the character fit in better in that world because they have a real history, friends, enemies, acquaintances, memories etc. They are a real part of that world and they belong as opposed to some nameless stranger that just got plopped into the world 5 minutes ago.
I think some of the pre-EA Ultima games sort of took a balance between this approach by having the character basically supposed to be 'you' transported to another world and you get to pick what sort of character you are yet that character still has a history with that world, but that's a balancing act that is hard to do.
I know many will vehemently disagree with me on this, but honestly if I get a choice between a bland, generic Bethesda PC or one like the Witcher with a rich, fleshed out history yet I still get to make the choices and play his or her role, I will pick the latter every time.
I don't think a "good" writer will necessarily translate into a good writer for games…
I agree to a point but I think it depends on what they are doing. If they are doing whole scenarios then absolutely, the writer needs to take into account the player's role in that scenario, making that a rewarding experience for the player, and also any potential non-linearity branching off. Obviously if you are not a gamer and have no desire to ever be one that could be a problem.
If the writer is doing dialog, in-game books, background lore or things of that sort then I think a more traditional script or novel writer is fine and probably even preferable.