So various churches can freely pick/discard almost whatever they want besides the 10 commandments while Muslims can't exactly just throw away the Quran or Hadith (which are much more specific)..
Except Jesus said that he didn't come to abolish the law but to fulfill it, and not one stroke of a letter of the law will pass away. So he didn't change anything about slavery, mistreatment of women, etc.
> didn't change anything about slavery, mistreatment of women, etc.
The "fulfill" bit is rather ambiguous. AFAIK the most popular interpretation (certainly when it comes to ceremonial rules like not eating pork/shellfish/etc.) is that his intention was to "bring the law to its intended goal/purpose" rather than to maintain it in perpetuity.
So if the remaining Jews continue following the Old Covenant, but others choose to rather follow Jesus' 'New and Eternal Covenant', then where would this obligation towards Old Testament law come from?
You aren't bringing up the moral law.
Hint: there's parts about freeing slaves, about repatriating foreigners, and about fallow fields. It's really sort of awe-inspiring how our secular government is implementing Jubilee by fiat.
And teachings of Paul supersede the stuff from Jesus.