As long as you have enough low skilled people to fill the jobs (ideally, teenagers and depending on your politics, immigrants), this is absolutely true.
The problem is when you fall into a situation like the one we have now, where you have hundreds of thousands of people who had decent paying low skill jobs and lost them all at once (over 5+ years, but close enough in econ terms).
The right thing to say/do long term is 'we should provide adequate training to help these people maximize productivity, as it's a smart investment', but in reality you've got tons of hungry, broke voters on gov't aid, significant political pushback against the government being the one to invest the money in them, and not enough training capacity. You can't build a nursing school overnight from scratch, or triple the capacity of every state's licensing board... So you're a bit stuck, both politically and practically.
The good news is that as the economy grows/recovers, low skill jobs will eventually re-emerge, shifted to whatever sectors they're now needed in. The bad news is that there's ramp-up time for doing this, and very little political will to support the idea that the government should fund it. These people take tons of government aid, which isn't cheap, and they vote. This tends to push politicians towards more protectionist and pro-low skill job rhetoric, ceterus paribus.
I should point out that it's probably not a no-brainer to all economists and policy makers to do this at all, there's significant dispute on if/when/how the government should pick winners in individual fields.