Debt/war/penal/chattel slavery was not a particularly strong economic activity in Europe in the Middle Ages. What we're mostly talking about is agricultural serfdom.

I think the Church had a lot less to do with the end of _serfdom_ than the Black Death. The sudden population drop mandated that lords who wanted to maintain production had to steal peasants from other lords, and improve their own compensation/conditions to retain their own labor force. And so on for the rest of the economy as well.

This represented a massive transfer of power and rights downwards... for a while. The late 1300's and 1400's have some of the best conditions for the laboring class for the previous 400 years or the next 400 years. You can hear about some of the dark days to follow in England specifically in https://www.youtube.com/watch?v=2ec9Al5ezYs