Indeed, as it has been doing globally. There's no doubt that a pauper today lives like a king compared to just a couple centuries ago.
Perhaps by statement is better said as "we can't raise the standard at the same rate for everyone."
This isn't a universal rule though. Many countries have raised the standards of the poor in proportion to the rich. But you'll see fewer billionaire yachts or private jets in those places too.
The standard of living has been rising constantly throughout American history