Historically, it's a very significant cartridge in that it could be fit into a mass-produced, military, bolt-action repeater (the Mauser 98 action), while still being suitable for large African game, particuarly dangerous game. Prior to Mausers chambered in 9.3x62, the rifle preferred wherever there was dangerous game was a double rifle. Understandably, nobody wanted to load loose rounds into a rifle under duress. They appreciated the total redundancy of a double, but the cost of a British-made double was untenable for many. The military, bolt-action repeater of Mauser's design promised reliable extraction and feeding from a magazine, but the popular military cartridges like 7x57 or 8x57 or 6.5x55 were not up to the task of the largest or dangerous game. The 9.3x62 came to be trusted for those purposes and because of the much lower cost, it was wildly popular in Africa.
Of course, the British double rifle makers didn't stay idle. Most significantly, they produced the 375 H&H for bolt-action rifles, though it required a "Magnum" length action (and therefore still expensive custom rifles, though not as expensive as doubles). The H&H Magnum did offer superior ballistics to the 9.3x62, but it's not clear to me that it enhanced performance enough that one could do something with a 375 that they couldn't do with a 9.3x62.
The comparison to a 35 Whelen is a good one. They are very much alike in that both enabled large game performance from a standard military length bolt-action -- what we would call today a "long-action." The 35 Whelen is like the American 9.3x62, and very much a good substitute for a costlier 375 H&H on a magnum-length action. Similarly, the 375 Ruger accomplishes something similar, but without any decrease in ballistic performance numbers.
Here is the most enduring thing about the 9.3x62. It ushered in the bolt-action rifle as the hunting rifle of choice, even where game hunting does not meaningfully require a "dangerous game rifle." The adoption of the bolt-action rifle by hunters cemented it as the most popular rifle action in the world. And it was all percipitated by the 9.3x62.
Had this cartridge not come about, the bolt-action would have remained primarily of interest to the military and would have eventually been replaced by semi-automatic rifles. European and American deer hunters would not have seen the point of a magazine-fed repeater. But it's popularity in Africa and its low cost cemented its acceptance.
Personally, I find the bolt-action rifle ill-suited to hunting large and medium sized non-dangerous game, and I blame the 9.3x62 and the Mauser for why most hunting rifles are based on this military repeater or derivatives thereof inspite of their illsuitedness.
But the cartridge does have its place and I would not say it is illsuited for its purpose at all. I do not have any personal experience with the 9.3 or similar cartridges on game but I am interested in them. I am unlikely to hunt the large or dangerous game they are normally recognized for. I could use such a cartridge but only for Mule Deer and Black Bear (300 pound bears, and probably not much larger ones that occur rarely). Many people would think they are too much cartridge for that size game, but I frequently hear from users of such cartridges that the lower bullet velocities result in less meat damage. So the cartridge may be even more versatile than its commonly accepted purpose. But the rifle, the bolt-action, I still decry as poorly-adapted for hunting the game most people hunt.