It really depends on what you're talking about. Individual components can often be automated fairly successfully, but the actual assembly of the components is much harder. Even in areas of manufacturing where it's automated you have to do massive amounts of work to get it to that point, and any changes can result in major downtime or retooling.
AI companies such as Vicarious have been promising AI that makes this easier. Their idea was that generic robots with the right grips and sensors can be configured to work on a variety of assembly lines. This way a factory can be retooled between jobs quicker and with less cost.
Lookup lights out manufacturing. There are factories that often run whole days in the dark because there's no point turning on the nights if there's no one around
Not really. Although running CNC milling machines and lathes unattended at night is reasonably common. Day shift sets them up, and they cut metal all night.
Fanuc, the robot manufacturer, famously does run a lights-out factory, and has since 2001. It was the dream of Fanuc's founder. Baosteel now has a lights-out steel coiling facility. Both of these are more PR than cost effective.
There are many factories where there are very, very few people for large rooms full of machines, though.
AI companies such as Vicarious have been promising AI that makes this easier. Their idea was that generic robots with the right grips and sensors can be configured to work on a variety of assembly lines. This way a factory can be retooled between jobs quicker and with less cost.