In the course of my editing work, I read quite a bit of bad writing. Much of my work is non-fiction and it's relatively easy to clean up and polish the writing if the thinking behind is sound. Bad fiction is another category entirely because so much goes into writing a good book. It's not just a strong feel for the mechanics of English, which are helpful but can be easily fixed. It's more knowing what makes a good story and balancing a whole series of components.
A good novel or memoir requires more than dramatic events. One reason novels and memoirs based on the life of someone often fall flat is that much of our lives are mundane, which isn't very interesting. On the other hand, and stringing together just the dramatic moments doesn't completely satisfy because that isn't realistic. Many less experienced writers don't take the heart that fact that the narrative arc, that crucial plot component, is more than big happenings. It's about making a choice, a decision that alters everything, sometimes for the protagonist and more often for everyone involved. If you can't identify that choice or those decisions, your novel may not hold.
A good novel or memoir requires a clear division between the major characters (only a few) and the minor players. Gone is the 19th-century tendency to fill novels with dozens and dozens of major players. While it is possible to have lots of characters, we only want cursory details on those that aren't major..
Back story should be brief and absolutely to the point. The information should be something we really need to know about the main character and his decisions. Again, we do not want back story on minor players. Often, we don't even need to know their names.
Omit facts and data from back story or from dialog. Readers don't care about a lot of facts. They're reading fiction for enjoyment, not for education. It's important to give sufficient facts so that the reader believes the author knows what she's talking about but beyond that, skip it. Even if your novel concerns the intricate dealings of a the financial world or an engineering firm, readers want plot and character, romance and danger. They don't care about the percentage of a loan.
Avoid verbs of attribution other than "said." No commenting, pleading, querying. If you absolutely must, it's okay to have a character "ask" but the question form of the dialog should carry that.
Learn what passive voice is and avoid it like the plague.
Limit indirect speech to a tiny percentage of your text. If it can't be dialog, maybe you don't need it at all.
Of course, there are exceptions to all these ideas but if you follow them most of the time, you'll write better fiction.