Inequality between genders in Islam is a difficult subject to discuss without pointing out that many female Muslims in the Western world are afforded the same rights and freedoms as male Muslims -- indeed, Muslim women have achieved equality without being permitted to enter Islam's holiest sites.
That said, women are most definitely treated differently under Islamic rule as outlined by Islamic law, and there is no point of view that can deny this. Some would argue that women and men are inherently different and that it would be imprudent to ignore this, and this line of reasoning leads us to unpleasant situations like women being denied the same opportunities to achieve success as men are.
Millions of Muslims in the West find slavery to be barbaric and none of them own slaves, and not only that but one of the central tenets of Islam is donation to make slavery unnecessary. This is evidence of fairness, equality, and social justice not only being compatible with Islam, but encouraged.
That said, slavery is permissible in Islam under certain circumstances, and the primary basis for this permission is the profound lack of protection afforded to non-Muslims outlined in Islamic teachings. This is intentional and personally I hope it falls by the wayside.
Finally, criticism of the Quran is a touchy subject. The study of mathematics was regarded as being unable to bring perfection to the human soul, but many Muslims studied it nevertheless and humanity advanced in indescribable ways. Death was similarly regarded as an act of God regardless of the cause of death, but the study of medicine was defended as not being un-Islamic.
https://en.wikipedia.org/wiki/Bidah