It's slow and buggy (i.e. it jerks painfully while scrolling on modern touch devices, it's sluggish on the desktop even in Chrome and they broke spacebar scrolling!), the photo upload experience doesn't work as reliably, search is embarrassing for Google and the timeline still doesn't do basic things like clustering shares of the same item or sorting based on what you've found interesting.
When Google can't compete with Facebook on technical quality, you know it's because of a management decision rather than lack of technical resources.
> But a better social product means nothing without an active network of users.
Lots of people tried it but they just found a marginally QA-ed bug-fest for the first couple of years which was clearly designed with the top priority of providing Google's ad sales team with tons of data to compete with Facebook ads and building a quality product seen as a cost of getting that data rather than the actual goal.
Better in what way? G+ has confusing and horrible interface, it's slow, and keeps asking me to import friends every single time I open up the page. That's not 'better product' in my opinion.
But a better social product means nothing without an active network of users.