But none of that ever applied to gentiles. Not before Christ, not after. Jews today do not claim that non-Jews are obliged to, or even ought to, perform any Mitzvot whatsoever -- and that's despite generally acknowledging that there are universal moral laws which bind all "children of Noah".

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?