Not only that, but the number of protestants today who have Catholic recent ancestors (like grandparents or great-grandparents) is quite large. To me that indicates the problem is not a recent one although it may be aggravated these days.
I have a few ideas about this and I think they need to be seriously considered, although if someone was to accuse me of generalizing I’d have to admit that could be so. I only know from my own observations.
The nature of parish life in the ‘typical’ Latin Catholic parish is pretty anonymous. People don’t necessarily even know the parishioners in the pews around them, and when they don’t show up they are not missed.
The pastor would be hard pressed to be able to call most of his congregation by name.
This is more true of the suburban parishes than the compact ethnic enclaves in some city neighborhoods.
A deacon friend of mine called his own parish here in Illinois a “sacrament factory” and he is starting to appear very discouraged himself. Even with being one of six deacons he is severely overworked. When he goes on hospital calls he gets a long list of parishioners and most of them do not recognize him, and he does not recognize them. To me that indicates a large population which is barely involved for years, although duly registered.
The clergy are so busy as it is, the people who do not choose to show up are not pursued. No one rings the bell and the only mail is the envelope packet which comes right on schedule.
I think the problem lies in part due to the very large size of the parish. But there is little to be done about that now, that pattern was set a long time ago, and the situation is accelerating. Bishops are closing smaller less ‘efficient’ parishes and consolidating them into larger communities. It almost cannot be helped, but a by-product of this process is more leakage from the pews.