This is a difficult problem to want to solve. Some of it has to do with low income or joblessness. So this is the first focus I would set - make income easier to come by, more fair, more distributed. This in itself will not fix the solo state of people but it would alleviate some worries. Then we have to tackle the social problem. This is really difficult to want to solve. Activity helps, so the state should be able to encourage more activity overall. For instance, in my own youth I was physically more active, so you meet a lot of people through sports - that alone works fairly well. You can probably think of many more cohesive social structures and what not. I think it is a difficult to want to solve problem though. Not everyone uses social media by the way but is still isolated; Japan even gave some odd name to this.