I think the idea that a certain percent of jobs should be "manufacturing jobs" or "blue collar" is a fallacy rooted in nostalgia. The problem is that we talk politically about "jobs" like they're a product consumed by workers, which is false. A job is a position in an organization created naturally by market demand. When there's no demand for that job anymore, it goes away and there's no reason to prop it up artificially. It's like saying we need to keep producing fax machines or VHS players because wouldn't it be a shame if we didn't make those anymore.