My Parish is thriving with families and young people, 2000 plus on Sunday's. Lots of baptisms, weddings, 90 are being confirmed. We do have a Latin Mass, and other different masses throughout Sunday, it is the Latin Mass that is mostly attended by the over 70s. The others are packed with people standing in the back. If young people don't stay it is because once they leave home, it is too expensive for them to live in the area. That may also be the case with parishes with a lot of elderly people, their children have most likely moved away.  There are also many between 30 and 50, that do not feel welcome, as they are divorced and remarried, LGBTQ, have seen their parents divorce and treated horribly by the Church, because they do know the church teaching on issues like birth control and do not agree with it or they don't believe in the faith. 
Ours is a Parish that had been Jesuit, so the drive for Social Justice, is deeply ingrained and remains. We now have a PP who is a people person