Define "young." Most Catholic parents bring their kids to Mass with them, even as teenagers.
I don't know of many parishes that rely on "young males" 18 and over to serve at Mass, so I'm not sure what your point is.
Even in the old days, when I was serving Mass, most Catholic boys were not altar servers, and only a handful ever darkened the door of a seminary, much less ever reached ordination.
This "well, we've got to restrict altar service to boys so we'll have future priests" is an old wives tale, in my experience.
Groups like the Fraternity of St. Peter don't have enough room for all of the vocations they attract. The tree is known by it's fruit.