What?! Who's doing that? Plumbers and scientists are not interchangeable cogs. Big brain scientist won't make good plumbers and plumbers won't make good scientists.

And plus, so what if they would be doing it? Why do you make it sound like being a plumber is like being a leper somehow? The world needs plumbers too and they make a pretty penny. See that US warship that wasn't combat effective anymore because the shitters broke. You can't win a war with starbucks sipping scientists, you still need roughnecks willing to get their hands dirty, fight, build and fix things.

Devil's advocate: Only productivity gains, not the entire economy, are built on scientific advancement. But wages haven't grown with productivity in half a century, so the loss of scientific advantage won't affect wage growth, therefore the economy will be fine.

(I know it's not convincing, but it's the best I can conjure.)