Robotics alone can make employment obsolete, but add in AI and it's all the more true. This is a real economic conundrum that human civilization has never faced before.
The 40 hour work week was established due to the work of Henry Ford as he discovered that productivity quality dropped off after that many hours a week. The 40 hours wasn't settled upon because society/economy needed it, but because it was the most that could be efficiently provided by a quality worker.
Fast forward to today, and production can be maxed out with less than 40 hours of human work per worker. So fewer peolpe are needed to make things or the same number of people could work fewer hours for maximum production.
But then with less employment, how can workers make enough to buy what's needed? Unemployment goes up because fewer people are needed, and then homelessness goes way up like it is now. It's easy to then see the logic of concluding the world is full of too many useless eaters that should be exterminated with a vaccine.
But I'm not sure there's an ethical solution to a world where anything can be produced cheaply but without having anything close to the whole world working to produce those things.