I saw one spectulation that these recruitment issues are artificially created so our military has the excuse to recruit lots of new undocumented immigrants into our military.
The military has always been mainly white and male.
Trash white males, and good luck filling positions.
In the later stages of the Roman Empire, the Roman Army could no longer count on Italians and, later on, provincials to provide men. So they used barbarians from outside the Empire. We know that those barbarians brought down the Western Empire. As Mark Twain once said, history does not repeat itself but it rhymes.