Ronald,
While I did privately contact you, I will also say I believe the ability to stand the test of time lies mostly with the routing skill of the gca in any era, if he wants a simple answer. If a course survives 100 years with the same routing, more or less, even if it has had features rebuilt a few times, it has by definition, stood the test of time. Routing can be permanent, features rarely are.
The details do change from decade to decade, but for all the talk of modern guys raping the land because they know they can move the earth to correct faulty routings, I don't think that is very common. We try to follow the land as much as possible, and the additional earthmoving probably comes from building irrigation lakes and bigger features.
So, every era has its challenges.
-Early guys couldn't move as much earth, but had fewer environmental off limits areas.
-They had less play to deal with, and could put greens and tees closer together, which makes sense when golf was 100% a walking game, whereas modern guys have to consider paths and wayward golf balls more.
- Mid century guys and beyond had to learn to adapt technology to their designs as it became available, all while adhering to ancient design principles.
-And so forth.
Of course, if we are narrowly defining his question about accessing the land, I would say that has changed from walking and horse to walking and truck or ATV, etc. On a few projects, access might be by low flying helicopter. And, it may be morphing to drone. What can't you see from a drone, without having to deal with the occasional snake?
(OT, but the only gca I have heard of getting bit or ill on a field walk was Frank Duane. in 1965 he was bitten by an insect and was stricken with Guillain-Barre Syndrome, a debilitating disease that soon confined him to a wheelchair. I know Paul Cowley was bitten by a rattler (I think on a job) Ian Andrew was chased by a moose, but got away. But for all the times we walk sites, I don't know of any major problems arising from "accessing the site."
Sorry for the OT, couldn't resist.