An ending does not make up a story
A story is not just about its ending. This movie's story gives you 85% of its juice towards the end! That's pretty sad, considering most viewers would actually fall asleep (or leave) halfway or even at the start from watching this movie.
If you can't keep your audience's interest within 15 minutes, you'll lose them.
By the way, this reminds me of the movie named Birdy (1984, Nicholas Cage) due to its similarity in pace slowness and eye-opening ending. But I liked that one a whole lot more than this one.
Better luck next time.