Frank, I don't think you're missing anything. Rustic Canyon is a very good course, but its reputation precedes it.
My impression after playing was much like yours. I enjoyed it and would have had no qualms about returning, but I couldn't help feeling slightly disappointed after hearing all the hype.
A funny thing has happened in the years since. When friends travel to the LA area I find myself recommending it to them heartily, and when I recently listed the 25 courses I'd be most excited to play again I found myself bumping it ahead of a few courses that I love and into the final spot. Rustic Canyon didn't live up to the GCA hype for me, and that's not really surprising. It's a very good course in a major metro area at a ridiculously affordable price point, so it's not surprising that lots of guys who post on here would have a love affair with the place that might border on excessive. I've seen posts comparing it to Pinehurst #2 and calling it the most impressive course of the last 15 years, and it just can't live up to that kind of fawning. Nevertheless, while it might not be quite as good as some of the hyperbole would suggest, it's still an outstanding golf course. I won't speak for you, but if not for the unrealistic expectations that I suspect I carried into my round at Rustic I think I'd have been more willing to sing its praises afterwards.