It was set back economically at least 100 years. As for ruins, i'm told some of it was. Atlanta comes to mind. The rest was at the very least economically ruined and many were left destitute.
As for burning it all down, they still wanted it's production, so they weren't going to do that, but they did deny everyone the right to vote and they imposed ridiculous Federal regulation on everything while stealing everything they could get their hands on.
The South was the architect of it’s own destruction.