Quran 4:24 And Sahih Muslim Book 8, Hadith Number 3432
I don’t see how you see it as a degradation. The idea is explained in Qur’an that a captive woman doesn’t need to wait for her husband to divorce her (who is way far away and is on the enemy side). They will become lawful for Muslims once their idda period is over (i.e it is clear that they are not pregnant with their current husband’s child in which case there is an issue of who will support the child). Generally if the captives that can’t be freed (no one ransoms them nor can they support themselves) then either they do end up as slave until they can free themselves through proving their financial capability or if they have converted to Islam and willing to marry, they can be married off without worrying about divorce from their polytheist husbands. 36:40 – 38:10 https://youtu.be/U2OQNmPtVcI?t=2201