When I say "the question is meaningless", I'm saying that the question doesn't identify a gap in useful knowledge of the world. It might be a purely definitional question for which the answer boils down to a tautology, or it may identify a trick of logic that appears to be knowledge but is not, e.g. a paradox, or it might simply be nonsense.
I say the question "does God exist?" is meaningless because:
(a) it is a simple Boolean yes/no question, but its is asking about the relationship between two incredibly abstract concepts: "God" and "existence". To address the question, these concepts must be defined in precise terms; but being abstract, there is no suitably objective metric to measure their precision against. Therefore, in practice, any logically consistent answer to this question will be a tautology.
(b) the validity of religion is not actually dependent upon the answer to this question; the concept of "faith" precludes the necessity of empirical validation. If you are religious, you may consider it important to believe in God, but this is not the same thing as it being important that God objectively exist.
(c) formalities of thought aside, my underlying metric is how useful answering the question is, not how true it is, and I do not see useful value in answering the question. Asking the question, on the other hand, opens the door to interesting conversations like this one, which give us an opportunity to analyze, exercise and improve our thought processes, which is why I'm participating in the discussion so extensively. :)