(1)I think socialism assumes people need each other and that a system that allows a person to exploit at the expense of others will ultimately fail. (2)Socialism doesn’t need group think that’s not what it is about. (3)Ideally people can all have their businesses just nobody can become king of the hill cause people would share the success. (4)Capitalism leads to an elite few with most of the wealth while the majority live poor.
To varying degrees I disagree with all four of your claims:
1 - People DO need each other - at least to prosper they do. Infrastructure is just one example of such needs.
2 - Define "group think"? Unless you have an unusual definition, I think this claim is a red herring.
3 - This hypothesis is strongly at odds with recent findings in human motivations research.
4 - Every plausible economic system is a complex, man-made machine, and like all such machines, it's not reasonable or necessary for complex machines to run perfectly without needs tweaks and monitoring and fine tuning. If your claim is that a hypothetically pure, un-tuned, capitalist society will statistically always lead to the extreme inequality you mention, well that might be, in theory.
But in practice, any and all of these systems can be kept in a healthy balance.