The problem is most "idea guys" have really bad ideas
I wouldn't say that. Sure, some people who aspire to such a career do have bad ideas. But I've heard plenty of good ideas as well. At the end of the day, the quality of the ideas on offer isn't the real issue.
The problem is that there IS NO career path for "idea" guys.
If you are a game designer/director, you are not simply an idea guy. Your primary function is as a manager/organizer of a team of creative individuals. Even if you came up with the original idea behind a title, you are spending 90% of your time keeping everyone else on task, setting priorities, documenting the work being done, and doing a lot of talking and communicating. You'll probably spend a decent chunk of your time just ironing out relationships between the various members of your team. (one of the most common duties of all authority figures)
There has never been a career path in video games where all you do is come up with ideas. There probably never will be. As many professional game designers will tell you, an idea by itself is worth nothing. The practical execution of the idea is what truly has value. Without that, it's nothing but words.