I've always tought of myself I wasn't the best gamer, I was really bad at FPS and Action games. I tought it was because I hadn't sufficient coordination or agility, but nothing was less true, I just didn't think. The handling of a game is something you grow customed to quite easy, mastering that is a question of mind. Offcourse games like Quake take more than just thinking, it takes reflexes, real hand eye coordination but those are competive fps games, this is a singleplayer RPG we are talking about.
Actually I think that I am good FPS and Action player... so, I wouldn't have a problem with a Quake RPG. But unfortunately, there ARE people who think that pressing more than one or two buttons at a time in a hectic real time fight - and probably in FPS view - is challenging. There are also people who think that combining runes or drawing symbols into the air for using magic is challenging.
What we have to think about is: What is the game supposed to be? If it's a rather action based RPG-like game like Dark Messiah of M&M, fine... use a nice combat system. But if it's going to be a "real" RPG, you have to apply to the RPG basics... that is playing a role without having to really do the things you do with your character. Generally, this aspect is not paid attention to in most so called RPGs... which is a pity in my opinion.