Very good point. Social capital has arguably been under attack for decades.

> large extended families

There has been a continual anti-natalist push in the West for many years, from the propaganda side convincing people it's too much work to have kids, or that it will be way more fun to drink and party through your 30s than it will be to watch your family grow up and eventually have grandchildren; to the ever-more-easy access to abortion and birth control. Combined with the removal of all fertility-retaining social and religious structures around reproduction, the result has been a precipitous drop in the birth rate.

What is not shown, however, in articles like the recent BBC one is the actual demographic makeup of the population and the birth rate faceted by various salient factors. It's certainly clear to anyone looking at that data that the demographics in 2050 or 2100 are going to make the West look unrecognizable, as there has been a massive influx of groups that still retain all of the social capital you're talking about and all of the reproductivity-enhancing structures I'm talking about.

I'm all for people having control over their bodies and their reproductivity, but a complete picture of what happens to both one's own life and one's city and country is not made available to younger people who are making important life decisions in an individualistic, oftentimes solipsistic bubble. Later regrets when you're beyond the age of being able to easily have children can be turned to the profit of expensive fertility clinics, or simply silenced with quiet sadness and proxy replacements, whether they take the form of cats and boxed wine or other more expensive forms of compensation.

> neighborhood churches

As an ex-Christian myself, I understand the critique of Christianity-as-Science, i.e. Christianity as a system for describing the physical world, or history, or what will happen in the future is not particularly valid. However, by using heavily philosophical arguments to throw away the substance of the religion, the attendant social capital that went with it is also lost, replaced by nothing. A church is not just the words read inside of it; it's the people, the connections, the charity and acts of service, the volunteers that hold a community together and help facilitate handing the structure off to the next generation. All of this is gone, and while the critiques about specific implementations were valid, the critique of "getting together as people in an area and professing our willingness to be good people publicly to one another" cannot be made, at least not in good faith.

> civic groups, mutual aid associations

Note that these still exist, but they either have to be focused on utterly generic causes, or focused on particular minority groups (e.g. Chinese Benevolent Associations and so forth). In no way do I discount or discourage the actions of these groups, but it's worth noting that it would be optically impossible and even legally difficult to try to establish groups for the native or founding-stock populations in many countries in the West.

> Things are never as good or as bad as they seem, but it sure seems bad right now.

It's critical to remember that these situations came about in no small part because of policy decisions. It's not random, it's not unplanned, even if it is chaotic; it's the result of many hands' work, so like any complicated software system there may never appear to be any overarching unifying infrastructure other than what is papered on top of it by abstraction. Still, policy decisions like the 1965 Hart-Celler act have had ramifications that are felt in this exact way, and will continue to propagate both their negative and positive effects down through populations over time unless action is taken to prevent or revert effects that harm people and cities.