If the plantation system would have ended on its own, it should have been allowed to do so.
You can put the same statement to the South.
They knew it was going to have to end as well, the economics of it was kicking their ass, they just didn’t want to end it and blamed the North for their economic troubles because they were industrializing and the South wasn’t. Because even multiple human workers weren’t as efficient as machinery that didn’t get tired or sick or old or pregnant or escape. They also didn’t want to lose their capital investments either, by freeing them and making them equal people.