I also think the real name policy is one of those things that we give too much weight too in analyzing the service. Lacking pseudonyms is not the reason "average" people have not used it.
The effect at G+ was that there was a very narrow sweet spot for intelligent conversation -- you needed a large number (~1000 - 10,000 minimum) of followers to generate real traction, but past 100k, the ability to moderate threads was highly tedious. Lauren was (and is) heavy on the one tool he's got, the ban hammer, blocking people. The reasons often aren't that the individuals in question are doing anything particularly wrong, but that the dynamics given the other people likely to come to the thread will simply go haywire.
Or you end up with accounts such as The Economist whose posts are interesting but comments are invariably almost totally inane.
Google exhibited (and continue to exhibit) a profound lack of understanding of real community.
That carries over as well to G+ "Commnities" which are a complete fucking abortion.
The reality is that once a service hits a certain critical mass it's almost impossible to extract. Facebook, like Windows, is now a permanent fixture in the tech community, and like Windows, it will only go away by slow, eventual deterioration made possible only by the gross incompetence of the company providing the software.
People don't care how much better your software is, the inertia will keep all but the most tech-savvy on the inferior solution as long as it provides basic semblances of expected functionality.
Two things: As far as I know most people are fine with using their real name on Facebook, so real names on Google+ would not have been the big problem, it was real names on Youtube made a lot of people angry. Also, now that people can comment on Youtube with Google+, the quality of discussions hasn't improved, it's merely become different inane stuff like "Hey x, check this out" and other excerpts from chat-like conversations that have nothing to do with the video playing.
I don't think that anyone will argue that pseudonyms are important to the average user. However, they are important to a small but influential group of users. The type of early adopter that otherwise could've driven G+ upward.
I would attribute Google+'s failures much more to their abysmal launch strategy, which massively restricted otherwise-excited users from ever joining Google+ until it became a barren wasteland.
The end result was every article about Google+ carried with it some form of controversy, negativity or problem. Joe average might not care about the real name policy at first, but they do care when they're told it's broken, sexist, racist and dangerous.
I'm not saying the real name policy didn't hurt Google+. I'm sure it did, but I think it could have weathered that storm if it wasn't weak in much more important areas like their launch strategy.
Or worth being influenced by…
Forcing me to use real name means that I suddenly must be super careful about everything and control everything the same way as I control work. Not worth it.
On the other end my siblings, cousins, school friends and some more all kept their AOL/hotmail/yahoo mail or other chat service nickname, which for a reason or another was a nickname.
I think it really depends on how, when and for what someone first came to the internet. If it was for fart jokes, or activism, real name policy is a bummer.