Nobody likes to close parishes, of course it is always a loss. However, changing population patterns should bring a prudent reassessment and rebalancing/equalizing of resources, across geographic areas and age groups. The argument in effect is “we don’t need youth or young adult ministry, because we have hardly any of those people”.
In evangelical churches it is standard practice to hire a Youth Pastor, part time then full time, as soon as they possibly can; even if they are worshipping in rented quarters for awhile. The Youth Pastor not only serves the teens and young adults currently attending, but recruits new people.
There used to be a balance between “total priests assigned to evangelism, outreach, and education”, on the one hand, and Pastors on the other hand, who maintain the flock. In my diocese, almost all the priests are now assigned to maintaining the flock, and specifically, it is the seniors who are by far the greatest number showing up.
So St. A parish spends money to put a new roof on their half empty building, while St. B parish does the same thing, in their half empty building a short distance away.
In the long run, you can see where this leads. (I am 69, by the way).