Plenty of things are a matter of having different values. Eating meat, going to church, drinking alcohol, owning slaves, stealing from each other, killing, making idols of things in heaven. Some of these, despite being technically allowed by religious customs (like how the Quran sets better conditions for slaves than what they generally saw at the time, and even encourages their release, but still allows for the practice) are bad despite the religious institution having previously been an improvement. And the others, like making idols, doesn't really matter if you're outside the religion.