It'll just chip away at the roles, it's not realistic to replace them for the reasons you've listed. However the point being made is that the expensive jobs are

It'll just chip away at the roles, it's not realistic to replace them for the reasons you've listed. However the point being made is that the expensive jobs are a more attractive target. That said I think AI/automation will still be involved, instead I imagine it'll be like what we already see with support/call centers: All the routine easy to manage items get sent to automation, while the complicated issues actually go through to a human.