The 30-06 is adequate when used properly, Phil. As you know Marg got that huge bison bull with two 180 gr lung shots, standing offhand at around 150 yards, and it was all over in seconds. Nothing lives long with shredded lungs.
The same day, not far away, another bull needed eight or nine rounds, first from a 350 Rem Mag, then a 300 Win Mag and a 338 Win. Good shot placement is always the first consideration, and if a hunter is afraid of the rifle, or not familiar with the anatomy of the animal, things may not go well.
A 30-06 in the hands of someone who knows how to shoot it may not be the Ultimate Yukon Rifle, however it is certainly adequate for everything from sheep in the mountains to bears and bison in the bush.
Ted