Cuz these economists look at wealth in aggregate, but look at behavior by market segment.

Asset prices have been skyrocketing. That only really helps people who have assets, but it still brings up the average enough to make the economy look it's doing great overall even despite the consumer price inflation.

So if you see that young adults are moving back in with their parents while living in an economy that is, in aggregate, "the strongest it's ever been"... you can only explain it as a matter of preference.