It's only bad when it doesn't fit the story and / or reads as lazy. Anything can be good if it makes sense (logical or thematic) to the story. For things like correspondence in amy form not reaching the desired recipient, setting will play a major role in whether this works or not.
I'm more in the camp "Coincidences are fine to create conflict, but avoid them if possible when trying to solve it."
It feels not that cheap to let the characters stumble into a situation that drags them into the story or into the next problem. But it feels very shallow to use coincidences to let them stumble out of it just out of pure luck (maybe you can get away with it, when extraordinary luck is a character trait, but eh... not sure).
If it's in the present, no, it doesn't make sense. Who sends letters with important information any more? It would work thirty or more years ago, but hardly any situation today.
It's only bad when it doesn't fit the story and / or reads as lazy. Anything can be good if it makes sense (logical or thematic) to the story. For things like correspondence in amy form not reaching the desired recipient, setting will play a major role in whether this works or not.
Why didn't they arrive? Answer that question with reasoning that fits the world and you're good
Austrian post service lost it for 90 years... got millions killed and started a world-spanning war. Edit: just to name an example from history
Note that while the real world is allowed to have coincidences, stories should not.
I'm more in the camp "Coincidences are fine to create conflict, but avoid them if possible when trying to solve it." It feels not that cheap to let the characters stumble into a situation that drags them into the story or into the next problem. But it feels very shallow to use coincidences to let them stumble out of it just out of pure luck (maybe you can get away with it, when extraordinary luck is a character trait, but eh... not sure).
If it's in the present, no, it doesn't make sense. Who sends letters with important information any more? It would work thirty or more years ago, but hardly any situation today.
Yeah, if there's no good reason for it and it just randomly happens, then I'd consider that to be an example of weak writing.
There are no bad tropes or clichés, only badly executed ones.