You make a good point in that poor catechesis is largely responsible for the difficulties that people have with the Church.
There are not more than 100 people in the world who truly hate the Catholic Church, but there are millions who hate what they perceive to be the Catholic Church. - Fulton Sheen
There are probably some who have actually chosen to leave based on some doctrine on which they disagree. For example, the Catholic Church does not permit artificial contraception or in-vitro fertilization. The reasons are spelled out but, unfortunately, some Catholics simply disagree and choose to leave for those christian churches that allow such practices. Sadly, the majority of Catholics who have left did so out of ignorance. They were never properly formed in their faith and, out of ignorance, switch to some other christian church that has caught their attention.
Agreed. Consider that this effort is called "Catholics Come Home", lending credence to the idea that these non-participants are (still) Catholic. Meanwhile, many überCatholicsTM will cite latae sententiae and various canon laws to argue that these same people shouldn't be considered Catholic at all. So if the überCatholicsTM are right, what kind of message is this ad campaign really sending?
This catholic left because I’m sick of the church turning the other cheek on abortion. Despite what they church says, it really isn’t against abortion. This greedy church is all too happy to not risk $$ from abortionists. If it were true to its own teachings it would excommunicate every last pro-abortion catholic. And would never have allowed the abortionist-and-chief to go to Notre Dame.
“I would suspect that the vast majority of those that have left the Roman Catholic Church or have stopped attending did not do so because they were unfamiliar with the teachings and practices of the church.”
You are underestimating the general lack of good Catholic teaching in the US for decades and decades.
Freegards