The US didn’t get less productive per hour of labor between 1950 and 2024

The point is that post-WWII is not the "normal" state of things. It was largely the result of a war that devastated every other major economy in the world, reducing competition from other countries. That gave the US a huge advantage. In addition there were strong government reforms from the pre-war depression-era time and reforms from during the war that curbed the excesses of the ultra-rich. The depression-era policies and the war-time policies also had the government playing a much more active role in the economy. Finally, this happened in a period where the world was much less "globalized" and relied on exploiting developing countries to a much greater extent than today.

Unless there's another devastating war that destroys every other major economy in the world, the US is never going to get the post-WWII advantage back. That was a big part of the reason a guy with a high-school education could support a family of 5 immediately after WWII. (Also, that mostly was the case for white guys, because the US post-WWII was a very racist country where the things like the GI Bill, which allowed veterans to get very cheap houses, was unavailable to non-whites.

The post-war period was one when the United Fruit Company convinced US presidents to orchestrate a coup in Guatemala in 1954 to remove the democratically elected president and install one who was more friendly to US international businesses. This meant cheap bananas for the US, big profits to US companies, and political violence and instability for Guatemala. So, the high-school educated guy supporting a family of 5 on his own was partially made possible by the exploitation of other countries by US-based businesses. I don't think anybody on the left wants that era to come back again.

But, it's possible to get the government to play a more active role in the economy again. For instance, in 1946 the top tax bracket was effectively 91%. Today it's 37%. Then there's enforcing anti-competitive statutes, going after all the monopolies, duopolies and cartels currently squeezing every American resident. Ideally, there would also be reforms to copyright laws that removed power from the entertainment cartel and handed it back to artists, or shortened copyright terms handing the fruits of copyright to the people.

A (white) guy with a high school education supporting a family of 5 in reasonable comfort was a historical anomaly. It relied on some good things like the government acting in the interest of regular people, taxing the super rich, and regulating large businesses. It relied on some shitty things, like the government helping out US-based businesses by orchestrating coups in other countries and otherwise aiding in the exploitation of developing countries. And it relied on some historical quirks, like the US being the only major participant to escape from WWII unscathed.