i can only speak for myself, but yes, the end did spoil all that for me. Trying to think of a way to put this that isn’t a spoiler...not a single storyline paid off, characters did about faces with no real build up, and the “winner,” wasn’t on anyone’s most wanted to rule list.
I don’t know your genre, so picking an example is hard, but imagine sitting through 3 hours of Titanic and, with everything the same up until the “car sex” scene, suddenly Jack is miffed the rich folks have it better and don’t like him so he busts into the wheel house to deliberately drive the ship into the iceberg saying he and Rose can fake their deaths and live together, Jack then jumps into a lifeboat, Rose jumps in with him and shoots him dead. As punishment she is sentenced to live the normal life she actually craves, her jerky ex fiancee Cal dies a rich old man in the arms of his loving wife and her side character no on really enjoys watching mother winds up with the big blue diamond. How are we feeling about the previous hours spent watching that movie?