Yeah, but even once we've achieved a society in which existence is inherently justified, some things are about the destination and some things are about the journey. We need to organize society around producing people and lives, good lives, as the final economic output. A person we "produce" under such a system will probably be highly skilled and want to participate in society's productive processes, because mastery and participation are real human needs for living a good life.
The question is how we distinguish between processes that are important to the people participating in them, and those that are not. Factory work was and is a massive improvement over subsistence farming, but no population in world history has been permanently satisfied spending their lives on the assembly line, so either we can take advantage of highly automated manufacturing to just have machines do the work or we can redirect automation towards re-involving human craftspeople into producing less interchangeable, higher-quality products (the market has been moving towards customizable commodities anyway).