Technical innovation increases the productivity of labor in industry. If production shouldn’t be wasteful, there needs to be a reduction in workers. Where do all these workers go if there’s no unemployment? In a capitalist economy the workers are left to die on the streets but in a socialist economy they need to get a job again, right? Does the state take the burden of cost of reeducating these workers to enter another field and factor this into calculations when introducing new technology?
For a vision of how advanced socialism would look for working I recommend ‘news from nowhere’ and the fiction section of ‘half earth socialism’ (which is basically an updated version). In summary there are no “jobs” as they exist now. People just sign up for stuff because they like doing it.