it literally has one of the worst endings in TV history.
no spoilers: the show was basically a scam in a sense that they claimed that they have explanations for everything when actually they were just making shit up on the way and wrote themselves in a corner. so they just ended with some broad "this answers everything" ending. this is not the actual ending but it's a bit like someone telling you some mystery story and then just ends it with "this was all a dream" instead of solving it.
also the makers are defending it with "it was about the characters and not the mysteries all along", basically if you care about the mysteries you will hate the ending.
if anything its worth rewatching just to experience season 1 finale and season 2 opening. that's top-tier television.
i honestly dont remember if kate dies, but i agree. the whole love-triangle is annoying as fuck and unrealistic, what kinda woman would choose virgin jack over CHAD sawyer????