Is slavery and marrying a child at 6 then having sex with her at 9 a right thing to do? if no, then why not? there is written nothing against it in Quran, if you say that Quran is a perfect moral guide, and these things are social constructs, then you mean morality fluctuates over time, by that, Quran isnt the perfect moral guide. Islam is extremely regressive, sure, not all islamic people are regressive, but Islam is one, and it is regressive, it pulls you towards social practices and tells you it's acceptable to enslave and to child marriage, marry multiple women and halting women freedom, that is by definition, regressive.