to me, it's really just the ending that makes more sense within the story (feeling realistic/natural instead of just checking a trope list) but sometimes writers (looking at you, rom com Hollywood) just ruin the ending by shitty dialogues. also sometimes it'd be a happier ending if the couple didn't come together.
I love tragic sad endings, I love happy endings, I love bittersweet endings, just really depends on the context of the story. (same goes with open endings, cliffhangers, and ambiguous endings)
I think execution is key.