iMo, both topic are like a bad penny, so, let me set the record straight on both topics ...
re: has the medium and its apparatus changed as the result of the introduction of the digital picture makiing era? .... Granting that the tools of picture making have changed, the simple fact is that good pictures are not about tools. Good pictures are about seeing and its close relative, vision and good pictures are what picture making is all about - same it ever was.
ASIDE: What is a good picture? The most direct answer to that question is that a good picture is one which pricks the eye and sensibilities of the viewer. But of course, that means many different things to many different people. Art critics, opinion makers, and trend setters aside, what is a good picture is all in the eye and mind of the beholder. Or, it could be written that one does know how to describe what is a good picture but one knows one when one sees it.
CAVEAT: That written, it must be rememebered that, as the Roman poet and philosopher Titus Lucretius Carus said, "quod ali cibus est aliis fuat acre venenum" (what is food for one man may be bitter poison to others).
re: the rules of photography, printing,etc. .... getting right to the point, these words from Sir Ansel express it all; "There are no rules for good photographs there are only good photographs." Or, there is the opinion of Edward Weston; "Consulting the rules of composition before taking a photograph, is like consulting the laws of gravity before going for a walk."
Or, as I might state it; "I don't need no stinkin' rules."
That written, it could be accurately stated that Sir Ansel had rules aplenty for making his pictures (the Zone System, et al). However, here's the important thing, they were his rules. He made them up in order to facilitate the making of what he considered to be a good photograph. And that exercise is precisely what any picture maker should do, make up rules which suit your manner of seeing and which express your vision. Every other rule is unadulterated crap.
In conclusion ... 1) the medium of photography and its apparatus (conventions) are the same as it ever was - John Szarkowski, in his book The Photographer's Eye, made clear (to the thinking mind) that photography is and always has been about the same 5 things: the thing itself, the detail, the frame, time and vantage point. iMo, he got it right and I simply can not see what has changed.
2) there are no rules for making good pictures, there are only good pictures. Some have opined that a picture maker should learn the rules and then learn how to break them. Seems like a waste of time to me. iMo, one's time is better spent learning about and understanding how one sees - something that comes from the inside, not from external influence. It's sort like Intuition vs. Rationality ...
"The intuitive mind is a sacred gift and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift." ~ Albert Einstein