I actually don't think Moose should be in the same basket as bear or elk. And there are some severe differences when you lump elk and bears together.
However, is the .338/.340 and up crew needed? IMHO, no - but - you end up limiting your shots due to the cartridge/bullet combo as opposed to your skill level. I think that the .30 and below crowd will kill very well at closer yardage. My personal limit is right at 300 yards. I would want a .338 for the 200 yards and beyond shots due to the additional smack.
Another factor to think about is time. I know several folks in Colorado that use the '06 as the big gun. They have the ability to pass on a longer shot as they are not pressured by time. For us common folk that have to use a guide as we are out of state, time may be against us. I want the limitation to be my maximum range not the bullet/cartridge's max. Those folks can pass today as they can be back tomorrow or the next weekend.
Not using an appropriate combo due to recoil is neck and neck with the same folks that refuse to practice with their rifles. Both groups are simply not paying their dues to hunt big game. Reminds me of an acquantiance that bought a 7mm STW for the "flat shooting" aspect and could not hit a coffee can at 100 yards with it. Truly a hardware solution to a software problem.
Game habits have changed and hunting ethics have also. The old timers had game that was closer and less wary. Rereading some of the old accounts, you'll note the horribly frequent mention of chasing wounded game. IMHO, this was the result of using inadequate equipment.
YMMV,
Giz