"When adults are learning to read, nobody hands them a pre-primer that a young child uses in learning to read."
Perhaps, neither are they handed an article from Lancet or JAMA, however.  "Dick and Jand" was an analog anyway.  Replace it with whatever learning tool you prefer and my statement about learning the basics stands.
"Neither the Baltimore Catechism nor the Catechism of the Catholic Church are the Living Word of God. They are not Sacred Scripture."
Glad we agree; as I said, they are summary not the sum.  They are timeless to the extent that they impart the kernel of the true faith, even without the deeper explanation of why it is true.
Canon Law is not a summary of faith - I don't even know why you are bringing it up.  Does it surprise you that some laws change and some do not?