On the one hand individuals owning land is largely illusory today anyway since property taxes are effectively paying a lease to the state despite supposed ownership. On the other hand if the state clearly and plainly owns all land outright and leases it to individuals then the state gets to decide who gets to lease which land. Taking the land someone is living on as is currently called eminent domain would be as simple as not renewing a lease. In order for the state to own all land it'd first have to take all land in the largest eminent domain grab ever. This is entirely at odds with the sole legitimate roles of the government, the protection of life, liberty, and property. In any event implementing such a system would involve a lot of shooting and death at best.