For me, part of the problem is that I think that it's a bit late in the game to compete with Facebook, and people are expecting G+ to be populated and integrated overnight into the same level that Facebook is now.
I liked G+ when it first came out because it was new and I hoped it would become a less noisy place in comparison to Facebook. But, then I realised, that was more about how I used Facebook -- and so I fixed that.
My friends list on Facebook is made up of a lot of deviantART people, and a smaller number of friends who I went to uni with, former school mates, family and people I play in the band with -- I've adapted how I use it to be a place that's no longer just an extension of my work environment, but a place for me to connect with friends & family.
G+ couldn't give me that because it would mean converting friends & family over to another platform, and since they are not as tech-savvy and don't spend anywhere near as much time online as I do, it seemed pointless to even try. Facebook is already on their smartphones and if anything their use of it has increased over the past few months as we communicate more on there.
I don't see the point of comparing Tumblr to G+/FB either because they are very different beasts.
In addition, at the launch of G+ it felt a little bit forced in terms of people claiming it was such an awesome tool. Ultimately, we've got a multitude of ways of connecting, sharing and interacting online -- each platform will have it's pros and cons and you just have to go with what's best for you. One mans trash.. etc