Yeah, if you read it, you will find that the Confederate constitution is taken word for word from the US Constitution in most parts. But they made the wise decision of fixing certain clauses that have been abused.
was it wise to add Article 1 Section 9 clause 4?
The Corwin amendment passed by US Congress and submitted to the states for ratification:
No amendment shall be made to the Constitution which will authorize or give to Congress the power to abolish or interfere, within any State, with the domestic institutions thereof, including that of persons held to labor or service by the laws of said State.
The US government was prepared to place slaves in a perpetual state of slavery to induce the South to stay in the Union.
No problem with it. It just keeps the Confederate government from legislating on that issue. It doesn’t keep the states from doing so. After all, that is a State issue, not a federal one.