A story is a process whereby you transfer an idea in your mind into the mind of another person as smoothly and as easily as possible. To mix a few more similes, your writing blunders are like rocks in the ice cream. It slows things down, causes his thinking to be re-concentrated for an instant, and, at worst, makes you look pretty foolish, even ignorant. Think of these things as potholes on your dream boulevard to success as a writer. Editors usually chew you up on story structure, ideas, pace, and a lot of other stuff, but if your manuscript is just plain sloppy, THAT immediately places you into a lower bracket with him.
Editors are like water.
They take the path of least resistance. As for the reader, no one has ever been able to accurately measure the time required to infect him with terminal boredom. It could be nearly instantaneous. I taught technical writing to engineers, project managers and technicians for a few years. Forget the story.