1. If the community has "healing power", it can accept new broken members as long as they don't overwhelm the support system. Many hippie and religious movements work with some version of this idea.
2. A struggling loner might be so because of traits unattractive to general society, but attractive to the community. Pretty much all subcultures fit here.
Healthy communities exist. They are increasingly rare due to the massive shift in the way of living, but they do exist.