The economy is the last thing a sane and moral human being would worry about when there were slaves sold like chattel. There was only one small group of people benefitting from this economy, and it was the masters. The masters in the cities got rich off brutalizing and selling slaves. Having an entire economy dependent on owning human beings is an economy that deserves to be ruined. The only people who were profiting were the slave owners! The slaves got nothing!
It also incredibly dehumanizing to assume that former slaves wouldn’t know what to do without slavery. All new civilizations begin with nothing and then they make something out of it. New industries can crop up that don’t require the majority of the population to work for free. They can at the very least go to the Free Cities and find work there, or return to their homes before they were enslaved.
Daenerys have a responsibility in kickstarting these new industries and find a new form of PAID work for these people. But I will never, ever be pressed that a bunch of rich slave owners are no longer rich or slave owning.
It is certainly ridiculous that I or anyone should feel sympathy and sorry for a slaver who lost their means of getting rich at the total expense of their brutalized, dehumanized enslaved. Why? Like the enslaved were singing hallelujahs for being enslaved or had wonderful lives by being enslaved? It boggles the mind.