Morality entails obligation or the imperative to behave in certain ways.
If the only “end point is the here and now,” then you seem to be claiming that we have some kind of moral obligation to act in the way determined by humans in the here and now.
That would seem problematic if you want to allow those “codes of conduct” to change where other behaviours become obligatory in a hundred or a thousand years.
Tell me what those standards could possibly be and we can cut to the chase and just carry those out now.
I submit that you would have no grounds for proposing what those standards might be because you allow that they could be just about anything. But if anything could be the standard at any time, why am I obligated to live by that groundless standard here and now?
Makes no sense that imperative moral principles should be baseless and shifting for no reason except that is the way they are.
Ergo, your conclusion…
If there is no ultimate standard, then I have no imperative or obligation to live up to temporary codes of conduct as if they are morally binding. And if I have no such obligation, then neither does anyone else.
Malicious, sadistic dictators have no obligation because there is no “right,” no “absolute standard,” nothing by which they are to be held accountable. Their “code of conduct” is the one they choose to live by and they are no more wrong or right than you or I, according to your “no ultimate standard” conclusion.
It would seem to me that your moral standard is by default “no ultimate standard,” which means you have no obligation to live by any standard NOT EVEN the one you now choose.
As a moral agent then, your explicit moral conclusion is that you are free to live any way you choose and are not obligated to do or refrain from doing anything. That becomes your moral system, by default.
Oh sure, you can claim that is not your system because you have imposed upon yourself moral standards, but if you are completely free to change or alter those as you choose because “no ultimate standard” exists, then your morality is merely capricious and with just as much justification could be anything else.
Even sadistic, malicious, brutal dictators have their "standards,’ which may not be ultimate, but are NO better or worse than yours without a clear ultimate standard by which to assess or compare them. AND you hold there is no such standard.