I have never hunted with the 30-30, but my brother-in-law killed dozens of moose with his 30-30 (M94). He would fire a shot, sit down, have a smoke or 2, and generally find the moose within 50 feet. I don't remember ever having to track one he had shot.
I killed a good-sized bear with a 7.62 X 39, which is a fair bit lower in power than the 30-30, and my wife shot a huge cow moose at 220 paces with the same rifle. The key is shot placement.
So yes, the 30-30 is plenty of gun in the hands of a competent shot, within the limitations of the rifle. Now, it's true that today's critters seem to be armour-plated, because you need a 499 WhizBang UltraMag to go for gophers, but millions of moose, elk, grizzlies, black bears and polar bears were shot by the 30-30. My grandfather used to keep meat on the table with a 44-40.