I think it's less a shift in calibers than it is a shift is platforms. Everybody wants to carry an AR and are shoe-horning the cartridges so chambered into hunting roles. When I was growing up, the .223 and similar cartridges were considered medium range varmint cartridges that
could be used at short range on small deer. Now hunters slap in a 30 round mag and take off after 200-250 lb. hogs, and leaving lots of wounded ones out there. I saw on another forum where a hunter was taking his .300 BO chambered AR "out west" and wanted to know what load in that caliber would be best for elk.
That said, some of the other calibers chambered in the AR platform should be great medium range hunting cartridges for medium size game.
35W
In the 70's I came up to a hunting party who had a .22-250, a lever action, and an M1 carbine with armor piercing, plus a standing gut shot deer already half processed from the .22-250, and they were leaving. Too small no tag. Hunters of old weren't all that. If anything it was the surplus of WWII ammo which pushed the use of those rounds long after they had been superceded in the Army. When I started hunting in the early 70's the traditional guys were out there and I was the oddball with .308.
Now I have a 5.56 pistol for alternate season, 6.8 SPC for deer, and Im building a .375 SOCOM. The first is cheap plinking but $25 deer ammo, the second is $35 deer ammo, and the third? Will force me into reloading with $75 deer ammo. A 20 round magazine holds 9 tho, so, no, I won't go blasting away in the woods. Not at $4 a round. Nope.
In my experience I hear the bolt action guys actually doing that, the report is distinct compared to intermediate rounds, and the cadence is very clear as they rack the bolt and empty the internal mag. Those of us hunting with AR's here in MO have a ten round max, and for the most part I hear one or a very fast second shot. Not bang boom bang boom boom boom. I have frequently strolled over after they left their stand to see the results, no deer, 5 casings in the leaves, and at least 7 cans. Been hunting 45 years in the same spot and it's no better now than then.
At 68 I realize I was an outlier and early adopter, and those older hunters were just drinking and plinking. It was deer camp, and what happened at deer camp stayed at deer camp. They seemed to get by tho, and those of us getting attention were carrying HK91's, SKS, and 98K's. I now realize it was because the Agents hadn't seen one and were really just curious. We were the new generation in the 70's and most of us moved into AR's since then. Those traditional old guns? Slow to reload, unwieldy and ammo quit being cheap - no wonder hunters moved on. Don't miss them at all.