Do you believe in an absolute or flexible concept of morality?
Most "how to be a proper human" schemes become flexible in practice (pertaining to the individual, not any mobs or governments filled with "righteous mechanistic adherence" to the law). But if the formal version itself of one such scheme is already bulging with degrees of freedom (i.e, already loose and murky, rather than leaving it up "real life" to handle that) then it is suspect as a pile of quasi-arbitrary ####. That is, a stimulant for cancer, a collapse of even its pretense of regulated behavior, waiting ahead. A moving target isn't a standard; without a fixed beach to keep sight of we eventually stray / swim too far into deep water and either get ourselves lost or drown someone else. If the rules aren't idealized in the official descriptive format then we don't know what the devil we're being "flexible" about when converting them into action (or non-action).
And a document / doctrine that literally tried to detail its mutability for the sake of local conditions -- by listing all the possible contingencies and the applicable variable responses and consequences - even taking into account all the optional modes of feeling that the "moral agent" could be in at a particular moment ("sometimes I feel like a ruthless asshole, sometimes I don't", etc), and as well the sets of personal situations the agent might be in (married, in financial debt, etc) and the consequences outputted by this or that decision in regard to that - would be a micromanagement Hell indeed. Making a person into far more a robot than a system that bluntly issues universals and the arguments backing them up, leaving it up to the individual to work out entirely on his/her own what degree of coloring outside the lines will be committed in "real life" when the circumstance of "right now" and "right here" warrant it. (Which of course, he/she is bloody damn well going to deviate into unless destined for a crucifixion later on). Fortunately, such a gigantic tome would be impossible for anyone to assimilate to memory, anyway, apart from the rare mnemonic freak out there. So it's back to this illusion of a superficial facade for a "flexible framework" being classifiable as a "moral system", above.