It is not about replacing jobs, it is about production to supply demand at the lowest cost.
If you are economically independent, meaning you can by yourself produce all that you need to live, do you need a job?
Particularly your job does not become menial, but a job to grow as a human being, and hopefully contribute something to society at large or to another human being who may make the net big breakthrough.
If I can give you for a $200 cost the ability to feed yourself for life that takes away the need for a job to buy food, and now you are always fed.
If I can do the same for energy, now you always have energy to use to run machines which do work for you.
You can exist like the early agriculturalists and be independent of any outside structure for economic sustainability.