Having now read through some of this persons comments on the thread it seems a huge area of regret for them is that they didn't export the content before they closed their accounts.
That I can understand is upsetting much like not having backups of family photos and the drive dying. Why they did not export their content I do not know. Facebook, etc. have all had "check out" functionality for many years now, all before the pandemic hit.
Seems they rushed into closing their accounts rather than exporting and backing all those memories up and without any kind of plan on what to do to fill the social void it would great. As a commenter wrote in reply to them "I gave up eating McDonald's everyday but now I have no food."