My 2 cents...
Aikido is just one of many means to an end. Since each individual in this world has a unique way of understanding, each individual will respond to different means. So no, aikido is not for everybody, although it's benefits can be shared by all.
To a deeper part of this question I answer with another question...
Has aikido been there for everyone?
I don't know of others experiences but I have ALWAYS one of the few Blacks in the dojo (if not THE only). I often wonder why that is. I don't feel that aikido has been accessible to certain demographics. I am not saying that is a fault of the art that we study but it may be a flaw in how we as practitioners market or reach out to others of the various ethnicities. I believe that if aikido is to spread and become relevant in the future somehow we have to reach a wider audience than what has been the norm for the past 30 years.