Yep. Must have been the fact that every Catholic I know can't really explain them either. Every time I asked a Catholic in regards to a question I would have in regards to the Catechism, they couldn't provide and answer. Often, they themselves don't know what is in the Catechism. I'll grant that is possibly due to bad teaching on the part of these who taught them, but that also shows that these members of the "flock" are trusting in traditions without understanding what they believe or understanding the meaning of the ritual.
I'll admit that in conducting my own research, I have come up with some understanding of some of the beliefs of my Catholic inlaws. Some teachings I can understand, others I see as contradictory to the Bible.
The real shame of it though is that most of my Catholic in-laws have no idea what is in the Catechism, or disagree with it themselves (And I'm not talking about a small family. My in-laws are solid German heritage. We're talking huge family). I'm talking about "hardcore" Catholics who attend Mass all the time and supposedly went through catechism training.
I'll share this with you. When my family went to the Catholic church, I discovered one day that my son (only age 5 at the time) was able to mouth most of the opening of mass along with the priest. When I asked him what it meant, he had no idea, he just knew the words. I have found that most of my in-laws are the same. They know the words, but either don't comprehend or don't really accept, they just go along with the ritual.
You're right. That is a shame.
You gotta admit it's a lot to know off the top of your head. For example, I can't fully explain every Catholic belief off the top of my head -- I could probably do okay for a lot of things, but for a full and inerrant explanation, wow, that would require memorizing hundreds of thousands of words and likely getting some kind of degree in Catholic theology. (I can't recite the full text of the Bible either, believe it or not.) But I'm familiar with the beliefs and any beliefs that didn't seem obvious or logical to me I've looked into more closely to the point where I accept them as truth.
It's similar to mathematics, which I've also studied. Just because I can't reproduce a particular proof off the top of my head doesn't mean the theorem isn't legit. You study it, accept it, and move on.
Ideally we're supposed to be able to explain everything in order to evangelize. But most fall short of the ideal in many ways. And there is something to be said for coming to Christ with the faith of a child -- accepting and believing.