I played in a two-and-a-half-year Tomb of Annihilation campaign and it always seemed like we were making progress and we never lost sight of our goal - we accepted that "find Oralunga" or "find Omu" was a goal and that exploration was the means to reach it. And the places we found while exploring were, generally speaking, amazing.
I think the Death Curse can and should be there from the start. My objection to the Death Curse is that it spotlights the awkward "resurrection for the rich and famous" status quo in Faerun, which has such bizarre implications when closely considered - and makes the whole notion of death so radically different from the way we view it in real life- that it's generally better NOT to closely consider it. But once you get past that I'm fine with it.
The ONLY area I wasn't crazy about was Port Nyanzaru which just had too much going on - I felt like we couldn't walk a block without three side quests landing in our laps (and sometimes not particularly interesting ones, though). I think the DM should be careful not to inundate players here, as it can feel paralyzing to be pulled in so many directions at once. The low-level AL adventures for that season arguably offer a better level 1-4 experience than the hardcover does, and can be used with the hardcover.