I agree with the posts that attribute part of the decline to the general decline of religion in the US, and extreme emphasis on secular education, advancement, material goods. But much of the decline has to be attributed to the leadership of many of the orders themselves.
They appear to be heavily responding to a “magisterium” of the secular culture, specifically the secular media. Read their websites, their priorities are the same as those of CNN. If Gates and Obama promote Common Core, they get FANATIC for Common Core. They applaud a given bishop or pope if that leader happens to agree with them, but they are not influenced by that bishop or pope.
The problem is greatest among orders of sisters. I can’t speak to their own, private spiritual development, as I don’t know. But I can speak to the fact that local religious orders that once bore much fruit, including evangelizing people to the Catholic Faith, don’t bear any fruit now, even where they do have some active sisters left. Why would a young woman join a religious community committed to the beliefs of the NY Times, the Democratic Party and personal empowerment when she can do those things on her own?
There are a few religious orders forming, or growing, that are orthodox in belief, united to the Magisterium. They serve the poor and evangelize, whereas the dying orders may serve the poor, but never evangelize. But girls have to do some research to find these orders, usually out of town. Where I live, the established religious orders used to recruit from their own grammar and high schools, based out of enormous mother houses (now being turned into nursing homes).
Among orders of priests, it is more complicated, but to some extent this principle holds. The more a community is intellectually, spiritually and emotionally attached to the “Spirit of the Age”, it may gather more applause but fewer recruits.
Much prayer is needed for sisters, religious priests and brothers.