Other journals from the expedition began to become public, including Oates', in which he said, ""Myself, I dislike Scott intensely and would chuck the whole thing if it were not that we are a British expedition....He [Scott] is not straight, it is himself first, the rest nowhere..." A series of books came out after that criticizing Scott. In the last few years, the pendulum has begun to swing the other way, with defenses of Scott appearing. Most significantly, the role of the weather being particularly bad has been seen as a critical factor.
Still, besides the dog thing, there was the fact that Scott decided, at the last minute, to make the polar dash with five men instead of the four that had been planned for, disrupting the supply arrangements, particularly fuel, since it now took 20% more to cook everything. His insistence, against advice, on taking Evans, who probably wasn't up to the expedition and who was the first to die on the return, slowing them up, was another factor. He also continued to drag 60 pounds of rock samples, even after it was clear they were in a race for their lives.
Yet another factor was the fuel in the depots. The fact that fuel would be lost because of the leather washer on the cans had been noted by earlier expeditions. Amundsen knew this and had his fuel cans soldered shut. Scott ignored it and found less fuel than planned at his depots. Being low on fuel meant they couldn't melt as much water as they needed to stay hydrated.
Scott wasn't as careful in making his return route easy to follow, either. Amundsen had food cans painted black and dropped one every mile. Scott wasted time on a few occasions trying to find the path to the next depot. Scott hired a ski instructor for his men, but then didn't make them learn how to do it. This list goes on and on.
The other part of the story is that Scott's death was used to tarnish Amundsen, as if what he'd done in using the dogs was somehow unfair. He actually resigned from one explorer's club when the club president proposed a toast to the dogs.