I am an Alaskan Hunter.
If you were a super duper expert hunter like my hunting buddy - you could do everything with a 338 Win Mag like he does. He uses it on deer to brown bear - but - this guy grew up on a Montana farm with a rifle in his diaper. He does not practice. He does not go to the range. He does not find shooting much fun anymore - and the box of bullets he has with only 16 left - he has taken 4 big game animals with.
Me - I am not burned out on shooting like he is. I have a safe full of guns - kinda like golf clubs - you need the right club for long distance, and the right one to get out of the sand trap.
Deer and caribou are not very resilient animals - once hit in a wide range or places, they will go down. The trick is to give them time to die - don't go running up or scare them into a run after being hit.
Moose, elk, and all bears - you need to hit them hard with a big caliber that is going to damage vital organs and break bones. On bears - you shoot and keep shooting until it stops moving.
Deer and caribou - any rifle with 243 Win or 308 Win like power works fine. If you are hunting out west or in big open spaces - you should upgrade to something flatter like a 7mm mag or 300 Win mag.
Moose and elk - you would be foolish to engage one with anything less than a 30-06.
Black bear - especially medium ones - are also not very resiliant. I have friends who hunt them with single shot pistols - usually 30-30 or 309.
Brown Bear...... you can use a 30-06 or 300Win Mag as brown bear protecton - but - if you are gonna actually hunt one and sneak up on them (you need to look them over before shooting - even a good taxidermist can't fix a big rub area) you would be an idiot to have anything less than a 338 Win Mag.
They do not make one rifle that does it all. If they did - my wife would have bought me one and sold all the rest.
You cannot beat a bolt action 223 rifle for cheap long distance practice! I have taken 8-10 deer so far with this caliber and gotten one shot clean kills.
The 243 Win is more powerful than the 223 and is a good choice for a deer and caribou gun. Since you will always find wolves, coyotes and fox in places with caribou - the 243 is small enough to drop them and not tear the hide up too bad at all. It's especially good at long distance shots.
You need a light caliber rifle like a 223 to learn to be a good shot. If you practice on a bigger caliber you will eiether develope bad habbits, go broke, and not learn to judge how wind effects your bullets. You learn more shooting a small handicap caliber like 223 than with a flat shooting 7mm mag.