You're looking at the opening credits just from the point of view of what background information it gives. That's nice, but the main reason they're brilliant is how well they set the tone of the story. Seeing those classic cheesy comic book style images set against The Times They Are A-Changing set up what the movie is about so brilliantly. The idea of nostalgia, and the "good ol days" being lost and forgotten. And the amusing double meaning "The Times Are A-Changing" lyric.
The opening credits orientates the audience into the world of Watchmen. There's so much information and story to take in in a relativity short amount of time. It makes sense to spend time slowly setting up the world. If you just blindly threw them into a story like this, it would be a mess.
In a graphic novel, or a regular novel for that matter, it's different. You go at your own pace, and can even flip back if you wish. In a movie, you have no control over the pacing. If you missed something, it's too late.
I don't understand exactly why you don't like the opening credits. What's wrong with them exactly?
How did non fans react to the credits? Did they think it was a cool montage but failed too notice what was going on? That's something I wonder about. Does it mean anything to see Nite Owl punching a guy when the audience does not yet know who he is?
Why does it matter if they make the connection? If they'd just had a random superhero punching a guy, the effect would be the same. It's all about setting the tone. It's just cool to have it be Nite Owl for repeat viewings.