There is a difference between something being meaningless and something without meaning. The former is emotive and centralizes consciousness. The latter is a description of the neutral nature of the external world.
To be without meaning is to point out that meaning is projected on to the world by a meaning maker. It is a value judgement on the part of a conscious being.
To be meaningless is to forget that there is a judgement call being made. It is the projection of incredulity on to the world.
That is to say, what is being overlooked is that there is a meaning to the act of seeing the world as meaningless. The knee jerk reaction of existentialism separates out the internal world – the consciousness –from the world that the consciousness is inside, namely the so-called external world.