The basic idea of Google Circles - that we have small circles that we share content and engage with, was basically sound.

Google+'s misstep was to overlay a clumsy UI and load a lot of the work of setting up and maintaining those circles on the user. Neither do a lot of users have the clean line between "Close Friend", "Friend" and "Acquaintance" clear in their head.

No, that was the one thing G+ got right. It just wasn't good enough to make up for the other deficiencies.

Ideas are easy to be good. Implementation and upkeep is where Google usually struggles.