Actually I think G+'s timing was just fine. Sure, earlier would have been better, but in 2011 a lot of people were very ready for an alternative to Facebook.

Google did an excellent job of targeting influencers and creating a wonderful experience for a few million people in the first several weeks of the "closed" beta. While most of the advantages were indeed small, there was one very big carrot: the possibility of improving your SEO via G+. [Of course a lot of people don't care about this, but they influencers they were talking about disproportionately do.] Facebook got caught somewhat flat-footed; Zuck threw everybody into lockdown mode for a few months, and when they surfaced, the general reaction "this is the best you can do?"

So while I agree that the technical issues weren't a major reason (Hangouts might have been janky but Facebook didn't have anything remotely comparable), I really do think it was the social stuff that killed them.

- the nymwars turned off a lot of their most enthusiastic early supporters, and turned the overall energy negative at a crucial time

- the failure to create a developer ecosystem (due to the lack of a write API) left them unable to leverage their deep pockets for a longer-term war of attrition against Facebook