If “states rights” meant you could keep people enslaved with no rights, then wasn’t there something wrong with “states rights”? Or incomplete or problematic?
Perhaps I could see your point if anti-slavery edicts applied equally to ALL states and time was given to the southern states to restructure their economy. It did not work that way, however, as the Emancipation Proclamation was enacted in January of 1863, long after the war started, and DID NOT APPLY to NORTHERN or UNION STATES! So your slavery slant is invalid!
You are arguing for how the law "ought to be", not in regard to how it actually was.
Yes, Slavery "ought" never have been accepted in the newly founded United States of America, but had the founders not explicitly accepted it, they never would have acquired the Southern States in the first place.
They deliberately wrote protections for slavery into the Constitution, as I pointed out in one of my messages above.