I think you've called it pretty good, in your assessment. I'll omit cross-valley long range, but all in all, long-range shooting is an open-country issue, generally. And I'll stay with rifles one would rationally carry across country in walking-hunting...
I buy into the general limit of around 400 yards or so, because of your bullet-drop comment. More important, however, is the hunter's prior experience and practice in shooting at targets out beyond, say, 300 yards.
For instance, a guy who shoots a lot of Silueta and regularly hits a 500-meter Ram, offhand, has a different perspective on his abilities than somebody who sights in at 100 yards from a benchrest and doesn't practice at longer ranges.
And there's range estimation. Lots of folks can't tell the difference between 200 and 400 yards. I've watched 'em! I have a 100-yard backstop for the benchrest on my front porch, and a hanging plate out at 185 yards. I've been told they are everything from 200 to 500 yards out!
Most hunting rifles/cartridges have a "point it and pull" capability of around 300 yards. That is, if it's 2" high at 100, it's dead on at about 200, and about 6" low at 300. For a deer, then, out to 300 yards, point it and pull...
Sorry for all the wandering around in this...I guess where I've gotten to is that it's mostly a function of experience and judgement. Ain't everything?
, Art