Of course many Catholics have left the faith—they do nt understand the ongoing miracle of the Real Presence of Our Lord and Savior, Jesus Christ, present in the most Holy Eucharist. If they did, and if they truly love Our Lord, they could never ever leave!
But teachings in many places have been almost non-existant and heresies rampant such that many Catholics do tno know their faith.
The early Catholic Christians of the first 300 years of the Church had to be willing to give thier lives. What for? The Bible had yet to be compiled. It is the Holy Eucharist that is worth living and DYING for!!!
When you read the Didache or the early Church Fathers, one can see that they assisted at the Holy Sacrifice of the Mass. For 2000 years Catholics have followed Our Lord who said—Do THIS (offer Holy Mass) in remembrance of Me.
I had the great privilege of attending Holy Mass this very morning and Our Blessed Lord came to me in Holy Communion.
Ahhh—the wonder of it all!
Ave Maria!
You know, many times people leave the Catholic Church out of curiosuity, experiment a bit with Protestant theologies and come back to the Lord, strengthened.