I believe you are aware there was an alternative ending: Carlo stabs himself, which makes more sense than traditional Finale. Actually, I even saw this alternative ending performed live in an opera house. And it does not disappoint (well, obviously, you want to enjoy a perfect bloody evening since you went to watch a Verdi opera!)
Coincidentally, we are voting (in the other thread) for the best recording of the second opera from Il Trittico, so I would say that Il Tabarro has disappointing ending since it does not resolve the main conflict between Michele and his wife.