BrainF##k has even fewer keywords than Java, that doesn't make it simple.

I understand your point. Ruby and Python both have dynamic behaviour which makes it difficult to predict ahead of time what will happen when a program is run. In practice, however, the full range of possibilities is never exercised. It's not enough to look only at the language specification when you make these generalizations.

EDIT: TL;DR, essentially what matters is not the complexity of the language, but the complexity of programs written in the language.