This entire thread is interesting to say the least, so I thought I would offer up some of my opinions and experiences:
1. When I was a broke college kid, I won a Ruger American in 6.5 Creedmoor in a raffle. It was the only bolt action I had, and by dang I was gonna hunt. So I put roughly 500 rounds down range last summer and took it out and killed the bull in my profile picture last September. Now, I'll be the first to admit that a 6.5 Creedmoor isn't the ideal elk cartridge, but I wouldn't let it keep me from going hunting.
2. Whenever I hear people talking about banning different calibers, it blows my mind how many people don't know the difference between "caliber" and "cartridge." There is a GIANT difference between a 300 Weatherby Mag and a .300 Blackout, even though both shoot the same caliber (diameter) of bullet. Arbitrarily banning a certain caliber, to me, is pointless. The caliber is irrelevant, the cartridge is what makes the difference. We can most likely all agree that a .300 BO is not enough for elk, but should we ban all .308 caliber cartridges? Not if you ever wanna hunt with your .300 Win Mag ever again.
3. Beyond the argument of the importance of shot placement is the argument of foot lbs of energy. So many people say that a certain cartridge doesn't produce enough energy to kill an animal, but where exactly did that come from? Who decided those arbitrary numbers? Who signed off on them? I'm sorry, but if we all feel like 1500 foot lbs of energy is what is needed to kill an elk, it's not like that elk is gonna laugh at you if you hit him with 1450 and turn and look at you and say "haha, not enough energy, I'm not gonna die" as the bullet bounces off of him. We walk around and say "nope that isn't enough energy, blah blah blah" but who ACTUALLY knows how much energy is REQUIRED to kill an elk? Not preferred, but REQUIRED. At what point will the bullet actually NOT kill the elk, at what threshold?
Personally, I think so many of us have forgotten what is really needed to bring down an animal. We have gotten so wrapped up in state of the art scopes and optics, the latest and greatest whiz-bang magnum, premium camo, $1000 packs, ballistic coefficients, sub MOA groups, and lots of other things. At the end of the day, none of that actually kills an elk. What kills an elk (or any big game animal) is a gaping hole in a vital organ. Whether that hole is put there by a 243 or a 340 Weatherby is irrelevant, if that elk has a hole through the middle of his heart with a well constructed bullet, he is going down. Our grandparents killed lots more animals that we ever have or will with 30-30 lever actions and cup and core bullets moving embarrassingly slow. The important thing is to be confident in your abilities, practice a crap ton, and know when too far is too far. There's lots of people saying things like "6.5 creedmoor isn't enough at distance, the guys can't shoot that far, etc." But I bet if we were all honest with each other, there's lots of us on here who have no business shooting a 300 WM at an elk beyond about 200 yards, no matter how great the trajectory is or how much energy it has. People have replaced practice and abilities with using lots of powder and lots of bullet, but a marginal shot is a marginal shot, whether it's with the Creedmoor or the Win Mag.
Rant over.