State-owned enterprises are a hallmark of socialism and have no place in a capitalist economy, and whatever happened under Tito is a done deal, whether you like it or not.
You have about as much chance of arguing successfully for a return of land and property to the Serbian Orthodox Church as a Romanov would in mounting a similar case for restitution of his family lands in Russia.
It just isn't going to happen.
Privatization is a fact of life throughout the Former Yugoslavia, to include in Serbia itself, and isn't going to be reversed or impeded by any right-thinking government.
Perhaps you can use the same logic and tell to the heirs of Jewish property confiscated under Hitler that "whatever happened under Hitler is a done deal, whether you like it or not".
Such claim would make you popular in Nazi circles where you rightfully belong.
This is comparable to a U.S. state selling off Federal property!
See how quick the sale would be put down if Wyoming attempted to sell Yellowstone!