Not great, no. But considering they got down to as low as 13,000 only a couple of seasons ago its a good recovery. Particularly in a market that has a great deal of options in terms of entertainment in general let alone in sporting teams in which to follow.
If the Tahs continue on their way next season should see more of a return to the days where between 27-30,000 was the average with a number of games the topping 35,000.
It's the format that has the most opportunity to offer a fan the ability to actually build an attachment to the team. As good as 7s can be the best games cannot compete with a good game of 15s let alone an outstanding one. There's a far broader range of skills in 15s. Better characters. More physical, more tactical etc. Basically, all the elements I think many Americans would enjoy as opposed to 7s.
I think you're missing the mark. If pro rugby is to succeed in the US, you need to convert a good number of the general public (outside of people who are already fans of the game).
Some of the reasons you mention are exactly why the general American public WON'T jump on to the rugby train if 15s were to be the professional version. Sadly, Joe Six-pack doesn't have the patience to sit down and learn the nuances of tactical kicking or sit through multiple scrum resets or aerial ping pong. They won't invest the time to learn why a prop has great scrummaging skills or technique.
Conversely, 7s offers everything that the American sports viewer enjoys - end-to-end action, a premium on athleticism, a game that's easy to understand, speed, etc. Not to mention the ability for broadcasters to insert commercial breaks at halftime and between games (a not so insignificant factor).
If professional rugby ever gets up and running in the US, it will be through 7s, not 15s. This isn't to say that 15s isn't a great game - it just doesn't offer the commercial appeal that 7s does. Pro 7s may open the door for a future pro 15s league (7s serving as a "gateway drug", if you will). The final product may not be the Super 7s format, but it won't be 15s, and the commercial interests reflect that.