That's a good point. Yes a lot of cult worshippers are basically vulnerable people lost and looking for belonging. Some are young and from broken homes etc.
I studied gangs once, an argument is they also provide a family and sense of belonging/fellowship, and members are often from broken families too.
But you don't need to be "lost" to enjoy that sense of belonging.
The advantages of aspects of our society, such as specialization, are balanced by the losses we have in the social realm.
There can be aspects of socialization in our society such as nationalism, company loyalty and such but they're echoes of true belonging. Family, including chosen family, remains.
But as people have fewer kids, as young people choose video games and online chatting over hooking up, or even thinking about cohabitation we will be more disintegrated.