No one is too dumb for AA, but some people are too smart.
There is a saying like this around the rooms of AA, I believe it refers to people who want to do it their own way as opposed to the AA way. There are lots of sayings around the rooms of AA. Most of them have no basis in the 12 steps or the book, IMHO. This is not to say they cannot be helpful to some people, but I wouldn't go through a lot of mental gymnastics trying to understand it, or feel that you have to agree with it. My sobriety does not depend on catchy sayings or slogans - it is my responsibility to put the work in to stay sober.
And of course a lot of people sober up without AA. It took AA for me but there are other ways - lots of people on this forum are living testimony to that.