This viewpoint of Barks’ ducks seems very narrow to me, Jeet. The Ducks were some of the most well rounded characters in kids comics at the time… which is probably the biggest reason why they were so successful.
While the ducks were certainly capable of greed, malice and avarice… they were also capable of affection, generosity and heroism. So I don’t really understand an interpretation that paints them as flat and one-dimensional as Little Dot or Richie Rich. If this is your viewpoint of them, I suggest you read more Barks! Check out almost any of his many Christmas stories for some good examples.
While there are certainly some dark themes in Barks’ comics, implying an overarching darkness to them seems absurd to me in the extreme.
The Barks that wrote the duck stories was most likely a very different man from the Barks you quote from shortly before his death. My understanding is that his later years were a very dark time for him with the loss of his wife and some exceedingly unscrupulous business handlers. I don’t see this degree of bitterness in his stories at all.