I disagree. Communism translates easily and consistently into a 'way of life.' It's just that the actual way of life to which it translates is 180 degrees different than the way of life it professes to bring about.
LOL! I guess that's one way of putting it....
The point is, that it could only be an "idea," precisely for the reason you point out: Communism is based not how people really are, but rather on how certain people think they ought to be.
We know it's at root an idea because the fundamental basis of the system can be summed up by "If everyone would just... (whatever)." Communism isn't alone in this, of course -- ideological movements share this characteristic.
The problem always comes when people don't "just".