The reality is that progress tends to be a case of two steps forward and one step back. It's also reality that this is true in part because people come up with these theoretical ideals of equality or something and they sometimes don't work in practical reality.

Additionally, one way to spread religion is to be tolerant of the existing culture of the people you are hoping to spread the religion to. This is Christianity is associated with a lot of holidays that have seemingly inane and random traditions, such as Easter and Easter Bunnies and hiding Easter eggs.

What on earth do bunnies and hiding eggs have to do with each other, much less the risen Christ? Not much, but it's some pagan set of traditions that got tolerated by the Christian church and that's how you have bunnies and hidden eggs all wrapped up with the risen Christ.

https://www.history.com/topics/holidays/history-of-easter

Yes, I'm mainly complaining about the reverse happening with islam's spread (due to it being spread by wars). Instead of islam progressively adapting to each country's culture, it brought regressive practices with it.