Hi,
A couple things off the top of my head that are changes in perspectives amongst historians as well as the way that the discipline itself has grown.
Since the 1970s there continues to be growth in what some call “revisionist” history. Some mean that term negatively and other positively or neutral. In my personal opinion, the term on its base level is reinterpreting and reinvestigating historical periods, topics, and people through different lens. At its best, it is examination of the facets of the historical object because — well, history is complex. It is not historical negationism. I think this goes further to the belief by some that history even academic history (like museums) are not neutral as in the historian has biases and/or is trying to persuade with their work (which is not necessarily bad). The truth is that history grows along with new perspectives and new evidence.
Here are some ways the history discipline has expanded since the 70s:
So I would say one of the biggest changes you’d see in textbooks or monographs between 1970s and now is the variety of approaches to well-worn topics through different lenses AND with new findings. For example, not just the great generals of the Civil War but perhaps the German immigrant perspectives on the Civil War or concealed female military participation in the war. Hope that makes sense.
Or, to put it another way, if someone is writing a history of 20th Century history (that spills into 21 a bit) what era are we in? What were a couple of preceding eras?