[baryphonic]

I can't speak to Judaism or Islam (the latter in particular seems quite legalistic), but Christianity has the concept of "Christian freedom." TL;DR: A Christian is allowed to partake in any activity that is not outlawed by Christ as long as doing so does not cause the Christian to stumble or cause others to stumble. So whereas Islam or Judaism forbid consumption of pork, Christianity allows it insofar as it does not cause someone to stumble. Or take alcohol: it's not explicitly outlawed (though debauchery is), yet the Christian should probably have more self-control than to drink to the brink of debauchery. It's just a matter of personal governance.

So IMO, Christianity does indeed have quite a bit of subjectivity, but it's all calibrated around creating good and forging a tight knit relationship with Christ so we can better emulate Him to the world.