Dear Sister in Christ: it is so seldom that I find myself in disagreement with you that I feel that I must avail myself of this opportunity! ;-)
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Of course, that letter has meaning -- to the one who wrote it. By the same token, God's Word has meaning (it is His Word) -- whether or not we choose to read it!
That letter and the Bible are both "repositories of meaning" -- stored and encoded information that is capable of conveying meaning -- independent of whether or not there is a receiver.
Or -- did I miss a definition of "meaning" that indicates otherwise?
Certainly the message has meaning to the sender. And to the receiver it will also have meaning. Whether the two are the same, who knows.
The message, intrinsic to itself is just a message. The conveyance, a conveyance.
If I pick up a message sent by someone to you and read it, it will have meaning to me. Even then, it may not be the same meaning as it would have to you or the sender of it.
Creation itself is such a repository. (emphasis mine)
But God is not holding the conveyance accountable in Romans 1:20. He is holding us, the receivers, accountable.