[ghaff]

The reasonable upthread point is that, for some people, working and collaborating in the office gave them their social fix and they may not have the time or the interest to seek out social activities outside of work hours.

The answer probably has to be either live with that or seek out work environments more to their liking. Note that this isn't even wholly a WFH/COVID situation. For years, I've worked with a very distributed group of people. If I went into the local office pre-COVID, there would be people there but potentially I wouldn't run into anyone I knew and almost certainly no one I directly worked with.