"Yeah we freed them, but we were allowed to restructure our laws to keep them subjugated and continued to treat them as subhuman. So was it really worth it?".
Reconstruction should have, at a minimum, barred any supporter of the Confederacy from holding office again, or, even better, had the leaders hanged as traitors. Instead we let them continue just with "banned" slavery (except for as punishment for a crime).
We then allowed slave owners to write the laws to integrate formerly enslaved people into their society, and, surprise surprise, they structured the laws to benefit themselves and keep the formerly enslaved as second class. So instead of "was ending slavery worth it?". It should be asking "was keeping slavers alive worth it?" as we are still dealing with the consequences of that today.