PHILADELPHIA — The notion that Americans are lonely — very, very lonely, and anxious, and depressed, and therefore more at risk of heart disease, dementia, and stroke — has gained traction in recent years. It’s been called an “epidemic” and a “quiet catastrophe,” a particular problem for men and young people and adults and the elderly and pretty much everyone. The surgeon general recently proposed a “National Strategy to Advance Social Connection.” Millennials and Gen Z are navigating the dating world in this context, and they say the overall experience is not inspiring. In a nationally repres…