Why can't the Catholic Church just cut through the fluff and simply say something like this: "Through the teaching of Christ, we believe that the Church is a sure way to heaven. How others fare in that respect has not been revealed to the Church"?
I fully agree, and I'm sure theologically that is what the Catholic Church wants to say. However, I also believe during its history - especially when it was a significant political power - that it used the current wording to maintain control. "Once you've been exposed to the Catholic Church, you better not step outside the bounds of the Catholic Church or you're not saved. Why, even those Muslims we're fighting will be saved, but YOU won't because you left!" Powerful words of control, indeed!
Your summary gives a tacit "approval" to searching God via other ways. Other branches of Christianity, or even other religions could be considered as an acceptable path to salvation, and thus why stick with obedience to the words and dictates of the Catholic Church?
A lot of the Catechism is, I believe, a result of the Church's previous interest in being more of a worldly power than a spiritual one. And unfortunately, because of the Church's position that its teachings are infallible (again, I believe this stemmed from its desire to maintain worldly control over recalcitrant princes and kings), it is awfully hard to change without blowing its own credibility. Pride stops the Church from correcting its previous errors.