Gratuitous complexity builds over time. (And there is no subject area where I have seen such gratuitous complexity as with computers.)
I have always thought this was because either authors assume knowledge of the earlier papers and/or they have become "too familiar" with the concepts, but I could be wrong. In the later case, perhaps an analogy would be a singer who has to perform the same song thousands of times. When an artist sings it for the 999th time it may sound different and maybe there is assumption everyone has heard it before.
Whatever the reason, it is common to see the fundamental concepts either glossed over or not even mentioned in recent papers.
The exception to this, for me, where subsequent papers are helpful, is when they succinctly summarise prior research or track a subject area over time, e.g., annual reviews.
Anyway, when I am searching for older papers, it often feels "counterintuitive" since I see many people studying an area for the first time who want only the latest research. Perhaps an analogy here could be software. There seems to be a fascination on HN with software that is "new" and being changed on a daily basis versus software that is finished and has been in use for a long time.
A related idea is university textbooks. Many students believe they must have the latest editions, for a variety of reasons. However the changes from one edition to the next may be relatively small and easily summarized. IME, sometimes a topic may be more clearly explained in earlier editions. Reading the earlier edition's treatment of a topic followed by the later edition's treatment is sometimes illuminating in ways that reading only the latest edition is not.
In summary, I find it easier to read the old, 1-3 page paper that lucidly discloses an original concept and then build understanding from there, reading subsequent research, than to read something written, e.g., this year and assume that old research, by virtue of it date, is just a minor detail and no longer important.