Cargo cruises only attract a very select few people because it does not offer any amenities other than a place to sleep and food - that's about it. And since this doesn't appeal to the majority of the cruising public, you're probably not going to hear much if anything about it in a cruise forum.
But the destinations you have listed all sound very interesting. I would love to see most if not all of those. We recently returned from two weeks in Tahiti and while not quite as exotic as some of these ports, I can definitely testify as to how beautiful the French Polynesia area is. Amazing, to say the least. Plus, the food, the music, and especially the people make it a wonderful place to visit.