Regarding the "It's impossible to beat the Death Curse" thing, the time limit imposed is specifically about saving the life of the individual person who hired the adventurers. However, exceeding that limit just means that character dies and the adventurers don't get paid by that person - it doesn't create a "fail state" for the adventure. When I played this, about a third of the way through the jungle, our group had learned enough about what was really going on with the Death Curse to know that stopping it in time to save that one NPC would be nice, but stopping the Death Curse in general was the important thing. If we got there a few days too late to save that one NPC, that would be a shame but kind of irrelevant in the grand scheme of things.
My suggestions for improving it:
- For some groups, the story should be more personal. That may mean that the Death Curse is threatening somebody they love and care about, as opposed to a rich retired adventurer who hired them. It also may mean that the DM might want to change what exactly the Death Curse is and how it works. As written, it highlights the awkward "resurrections for the rich and famous" aspect of Faerunian society which narratively to be honest benefits from not being examined too closely instead of being highlighted as this adventure does. You might want to change it to just afflicting people at random, or just meaning resurrections are now impossible, depending on your taste.
- I loved the whole adventure EXCEPT Port Nyanzaru which felt overwhelmingly stuffed with side-quests (and often not very interesting ones). It got so that we were reluctant to walk down the street from one location to another because three more NPCs would run up to us and drop plot hooks on us. DM may want to exercise restraint here. The AL adventures for this season also provide a better start than the hardcover does.