I agree with the OP when he says, the .375 is not a "magic bullet." I would argue there are no magic calibers/bullets--only suitable calibers and bullets and good shot placement. A .375 H&H is adequate, as is a .300 Win. Mag. or a 7x57.
One thing that often catches my ear in a discussion like this is when people use a bang/flop as proof that one caliber/bullet combination is better than another. When an animal goes right down, it is impressive for sure, but a bang/flop is NOT the best measure of a suitability or effectiveness of a caliber/bullet combination. To me, the best measure of effectiveness is whether the bullet will get to the vitals (spine, heart or lungs) and retain enough mass and energy to disable those systems. A well-constructed 7mm through the spine will produce instant incapacitation of PG, whereas a .375 through the heart will not (and vice versa). On the flip side, an animal shot through the heart can go quite a way (increased adrenaline, possibly?) and rarely do they drop on the spot. Does that mean the shot or caliber or bullet was ineffective? No. It is just a different mechanism of injury.
One often overlooked consideration in rifle selection is recoil. Not from an accuracy standpoint, but whether the shooter can keep the animal in the field of view after the shot. In my experience, it is difficult to keep eyes on an animal after the shot with a .375 H&H at anything over 4x or 6x. Contrast that with a 7x57 where I can usually see my impact all the way up to 12x. Does that make the .375 H&H unsuitable? Not at all. Just a consideration.
To be clear, my comments here have to do with PG not DG.
One thing that often catches my ear in a discussion like this is when people use a bang/flop as proof that one caliber/bullet combination is better than another. When an animal goes right down, it is impressive for sure, but a bang/flop is NOT the best measure of a suitability or effectiveness of a caliber/bullet combination. To me, the best measure of effectiveness is whether the bullet will get to the vitals (spine, heart or lungs) and retain enough mass and energy to disable those systems. A well-constructed 7mm through the spine will produce instant incapacitation of PG, whereas a .375 through the heart will not (and vice versa). On the flip side, an animal shot through the heart can go quite a way (increased adrenaline, possibly?) and rarely do they drop on the spot. Does that mean the shot or caliber or bullet was ineffective? No. It is just a different mechanism of injury.
One often overlooked consideration in rifle selection is recoil. Not from an accuracy standpoint, but whether the shooter can keep the animal in the field of view after the shot. In my experience, it is difficult to keep eyes on an animal after the shot with a .375 H&H at anything over 4x or 6x. Contrast that with a 7x57 where I can usually see my impact all the way up to 12x. Does that make the .375 H&H unsuitable? Not at all. Just a consideration.
To be clear, my comments here have to do with PG not DG.