For me, the number one problem of Google+ was that many who were excited to try it, couldn't (for over a year, if I recall?). We were a 2nd-class-citizens with a Google Apps account, rather than a Gmail account.
I was just clarifying that the invite-only stage didn't last more than a year.
Slower, with a solid core community, would have been far better for G+ IMO. It opened up too fast.
Not only didn't it have a gelled community, but there were far too many UI / feature glitches and omissions. Many of which persist to this day.