Those kids will grow up to be out of touch with reality, thinking they're the center of their tiny universe while being hopeless at everything other than their field of speciality.
You have no idea what you are talking about. I homeschooled my kids and they have a larger and more diverse circle of friends than you can possibly imagine. Unlike school kids, their friends are also from a wider variety of ages because my children didn't experience the age-range apartheid that you would consider 'normal' where the majority of the children you would interact with each day were within 12 months of your own age. My daughter's 16th birthday party had more than 70 kids and 30 adults on the guest list - and these really are close friends who she has spent more quality time with growing up than anything you get out in the school yard between classes.
I'm a software engineer, but for university the kids have gone into fields as widely different as biotech, justice/law, arts/language and design. One of them went and lived in Beijing for a year to immerse herself in the culture/language when she turned 18. Another has travelled to Japan, China and the USA regularly since they were 17 years old. At 13 years old, one of the kids went and stayed with a friend's family in the USA for three months - even saved up the airfare on her own by doing babysitting around the neighborhood.
I guess that I wouldn't agree with the same homeschooling that you don't agree with - but unfortunately for you the reality of what the vast majority of homeschoolers are doing has nothing to do with your narrow prejudiced ideas. For every homeschooling parent who is keeping their kids in the basement, I'll show you 10 school kids who are wasting their lives and potential without any help from their parents at all.
It's your call.