Of course, certain individuals may enjoy and thrive in isolated environments.
https://www.cdc.gov/aging/publications/features/lonely-older...
Frankly, I believe those types of studies rreally about happiness with ones social life, not about ones social life relative to others. But that's just my take.
There are however negative health effects, and have been studied quite well.
Well, someone can smoke for 60 years, from 20 year old onwards, and never get cancer either. Actually, tons do just that. But lung cancer from smoking is not "stereotyping", it's a causual mechanism and a statistical reality.
It's not like that you mechanically and deterministically die or your health becomes predictably worse at the individual level.
Not to mention there's also the psychological health and the developmental effect.