isolation meant you were very likely to die
That's very true and one of the reasons we experience loneliness, but knowing this and I've known it for some time you can fight it. Modern humans have learned we don't have to give in to every primitive evolutionary response.
It's actually very pleasant having lots of time to read, think, go to the cinema, the theatre or walk in the countryside alone. It's also pleasant not having to think of other people's needs, just do what you want, when you want.
As you described our evolution and to some extent society also has conditioned us to fear being alone but we can beat the fear. I say these things for all those who are terrified of leaving the cult and have a terrible fear of being alone.