pg provided his own tldr; in the first paragraph of the essay:

"One advantage of being old is that you can see change happen in your lifetime. A lot of the change I've seen is fragmentation. US politics is much more polarized than it used to be. Culturally we have ever less common ground. The creative class flocks to a handful of happy cities, abandoning the rest. And increasing economic inequality means the spread between rich and poor is growing too. I'd like to propose a hypothesis: that all these trends are instances of the same phenomenon. And moreover, that the cause is not some force that's pulling us apart, but rather the erosion of forces that had been pushing us together."

In general he tries to look for a net positive outcome resulting from these changes, but is not confident there will be one.

Some unusual forces caused a temporary change in the US during the 20th century that pushed us towards equality and conformity, but these forces have largely eroded and we can expect greater fragmentation moving forward.

WWII had a cohesive effect on the American society and economy that lasted approximately until the 1980s. The results were more equality and less fragmentation during that period.

Since the 1980s technological progress and also social factors brought an ever increasing re-fragmentation, which, if not properly addressed, might lead to problems soon.

Acknowledging these problems is remarkable -- I think it's the first time pg did that.

An old man wants the time of his youth to return, and he sees the increasing individualism as an erosion of our culture. The world has changed and he wants the old one back because he understands it.

I think you could start here:

"By no coincidence it was in the early 1980s that the term "yuppie" was coined."

... and then read the remaining 15 or so paragraphs - that gets you the whole gist.

And they are made out of tiki taki and they all look just the same was a historic fluke.

A (mostly) golden age in the US was caused by conditions that forced the population to work together.

The conditions have disappeared, so the economic and social order is unraveling.

Let’s acknowledge the issue and let that acknowledgment guide our policy decisions. We want this golden age back(?).

World War 2 and large companies like GE and IBM kept everyone the same.