You talk as if white families didn’t directly benefit from the fact non-white families had less, as if it was only rich capitalists sacrificing so lower class families had more in that era.

No, I do not, you are misunderstanding or misconstruing what I'm saying. I am saying that the bigger factor was the partial disciplining of capital in the post WW2 era. I am talking about relative importance of multiple factors in achieving an outcome. To put it differently: white supremacy in the post-WW2 era was not more aggressive than in the past, so we cannot reasonably claim that the increase in standards of living for the lower middle class is attributable to white supremacy. White supremacy was in fact even more aggressive in gilded age. If white supremacy explains lower middle class prosperity, the gilded age would have been a better time to be lower middle class than the post-WW2 era. It wasn't, and it doesn't.

Same applies to the misogyny allegation. Women were even more repressed in the previous eras. Did that mean that a typical lower middle class white dude was better off before? No!

Again, I am being very careful here: I'm not arguing against dismantling off networks of power that intersect with capitalist domination here. I am saying that if you want to talk about economic standards of living, you have to talk about economic policy. Antiracism and antisexism are necessary but they are not sufficient. Without a socialist backbone, we know now empirically that they just get coopted by corporate shills and all you get the kind of "corporate diversity" of the Democrats.

Nostalgia is a tool of modern white-supremacism, and people should be more aware of that fact.

I understand the distrust of nostalgia. But I don't share it in the general sense. Nostalgia is a form of memory and it helps keep movements alive when they have been defeated hoping they can fight another day. The past is of course a space of struggle. Which is precisely why we should refuse to cede it to the far right. The answer to someone being nostalgic for a better quality of life cannot be to attack them for not mentioning that it was not good for everyone. Without nostalgia for their homes, the Palestinians would have long ago given up the dream of freedom. When they lovingly hold on to their house keys, they don't miss the imperialist, authoritarian, genocidal Ottoman fucking Empire, they miss not being dispossessed, displaced and oppressed by Zionism. Would it not be counter-productive to get in their faces every time they become nostalgic about the past with "yea but while you were cozy in your houses before the foundation of Israel, the Ottoman system you were part of was genociding Armenians and Greeks"?

Here you have members of the contemporary precariat pining for a time when they didn't have to work shitty gig jobs. Punching them in the face with the shitty things from the past is entirely counter productive. It in fact strengthens the fascist narrative because it reinforces the lie that in order for a white person to have a good quality of life, white supremacy has to also be in place. It cedes the past to the far right.

===================== EDIT, to synthesize a bit:

Postwar one-income stability was real, but it also wasn’t universal. The engine was political economy: high worker bargaining power (unions), regulation, and a state willing to tax and spend. When those institutions eroded, typical pay stopped tracking productivity. The distribution was racialized and gendered: a huge chunk of "normal" middle-class security was homeownership and cheap credit, and Black veterans and families were systematically blocked from GI Bill and housing pathways in many places.

So the honest slogan is: bring back the disciplining of capital, this time without segregation and patriarchal dependency.