Lots of people need assembly jobs. It is dignified work and is required in every society. Otherwise people are just selling doughnuts to each other, not necessarily a noble or sustainable model.
Or, you know, actually using their minds to create new ideas. I don't have a problem with manufacturing jobs, but let's be honest, if your job can be done by a robot, eventually it
will be done by a robot. And yes, even the jobs doing maintenance on robots will be done by robots eventually.
With robots and 3D printers (which are also robots), pretty much all human manufacturing has an end date on it, and we are headed there rather quickly. The only manufacturing that will have a value will be in manufacturing unique items. That means works of physical art, that means luxury goods made by hand specifically to increase its value (as items made by hand will be seen as particularly rare). Everything else will be increasingly manufactured without a single human ever touching it, with increasing quality and customizability.
The only jobs here to stay are the ones creating intellectual property, as somebody still needs to tell the robots what to build, and those creating new math (programming, physics, chemistry) to make the robots more efficient. Well, and the entertainment professions. We'll always need comedians, artists, writers, musicians, and actors. Scientists and teachers will continue to get shafted, but that's just how things go.