You make valid points; however, if a large portion of the congregation leaves en masse, I would have to conclude that there has been some sort of failing at either the parish or diocesan level.
The only instances I have seen of this are where the bishop shut down multiple parishes within close proximity of each other. Is there any surprise? No. He stopped catechizing them years ago, replaced their priests with Lay Ecclesial Ministers and then shut them down. Now he is preparing to do the same thing to another community. Catholics can tolerate just so much before they up and leave for greener pastures. And the Evangelical Churches are waiting for them with open arms.