Good callout with Google+

Google+ was in every measurable way better than Facebook. It was cleaner, faster, and had features that people claimed they wanted (to be able to have full control over which CIRCLES they share different info with)

And it completely busted because adoption of a social network is impossible without critical mass.

At the time it was because people didn't have a strong enough reason to leave Facebook.

Today it's because they wouldn't have a strong enough reason to leave TikTok/Instagram/Whatsapp/etc.