Only 1 verse or a few verses or just verses 23:5,6 alone doesn't make the Quran but all over 6000 verses, to get the proper understanding of Islamic principles and in their right contexts.
Also, it should be noted that for the sake of protecting/safeguarding the poetic prowess and eloquence of the Quran, to outsmart the pagan Arab poets of the time, certain Arabic words were omitted as per tradition, which if had been added to the verses would give us a clear meaning but otherwise would spoil the 'rhyming'.
For example see this ayah, supposedly added with the probably omitted word or words (emphasized in brackets)which shall give us the meaning in the proper context:
"If ye fear that ye shall not be able to deal justly with the orphans, Marry women of your choice, two or three or four; but if ye fear that ye shall not be able to deal justly (with them), then (marry) only one, or (marry a captive) that your right hands possess, that will be more suitable, to prevent you from doing injustice."
( سورة النساء , An-Nisa, Chapter #4, Verse #3)
Here it means a person can have sex with a slave girl only after freeing her and upon getting her consent for marriage in relation to other verses of the Quran.
What may differ is the 'dowry(bride money)' the man must pay the bride to be. It the case of a 'free woman', the 'dowry' may be huge amount. But in the case of the 'slave' girl, just freeing' the girl is enough for 'dower' to marry the girl.
Allahu Alam.