In my view, such claims have been grossly exaggerated. The fact is Muhammad's mother was not buried alive at birth nor any of his wives or cousins etc etc. Arabs used to have many wives and slaves girls. This would have been impossible if pagans had killed their daughters at birth at an alarming rate.
The lot of people in general has been improving always, for that is the way world works. People have been changing with time in various respects due to improvments in their knowledge and experience. This improvment continues even today. This is why ideas that were improvement in the past have become backwards today because standards for decency have risen to measure things by. So Islam or muslims alonecannot be creditted for such natural improvments. All movement in the world have brought about something better that was not their before them.
The quran mentions queen of sheba and we find in hadith accounts that muhammad's first wife, khadija, was a business woman. If the culture at the time was not sufficiently peaceful at the time then people could not travel about for business as Muhamamd used to. So the piocture portrayed about pagans of arabia by islamic sources is controversial to say the least if not hugely exaggerated.
Perhaps, muslims did so to create a contrasting situation to raise muhammad above others. Muslim have the habit of saying that pagans were ignorant people when it suits them and very knowledgable when that suits them. For example, one may have heard muslims saying that pagans were so good at language and poetry etc yet could not produce the like of the quran. This they do to show that even very knowledgeable people of time could not meet the challenge of the quran 2/23 etc. Perhaps they think that it would be embarrasing for them to claim that pagans were ignorant and illiterate so could not produce anything like the quran, for then the challenge would look absurd ie what is the point of challenging somebody who is not even capable of understanding the nature of the challenge? That would be like an adult challenging a new born baby to produce an encyclopedia .
So when one refers to islamic history, one needs to be self critical to some degree to see that one is not making any claim that opposes reality of life as it is before our very eyes.