True, we should have been doing a lot more evangelization all along. Yes, there are some people living around those parishes, but a lot fewer than before. The parishioners are often older people living in the suburbs. There’s a part time priest or deacon holding the fort, sometimes a food pantry.
It would take a diocesan subsidy just to pay the heat bill, forget preventive building maintenance. I love old churches, whenever I travel my wife and I see every historic church we can. But keep in mind there are many Catholic youths and young adults who live far from the historic churches, many of them have drifted away or are at risk of doing so.
The diocese has a responsibility to reach out to those people, develop outreaches in the suburbs and to young adults. The seniors, and the historic churches, are “the squeaky wheel” but sometimes you have to shift priorities. That takes money, priests, and deacons. Almost all our priests and deacons are mostly assigned to parishes.