One of the most important tools a writer has is honesty. Honesty is the light that can bring people together and let others know that they are not alone.
Write your truth. Don't pull any punches. Don't write what you think others want to hear.
Write your truth. By doing this you'll discover that your honesty will bring out truths that are both universal and meaningful.
Also - try to uncover those nuggets of truth within each of your characters. Maybe not all of your characters share your values or your own particular truths - but remember that a well written villain is never just a villain. A well written hero is never just a hero.
Sociopaths have aches and dreams.
Saints have inner demons and regrets.
I'm not saying you must make your readers love and adore your villains - just make them feel your villains.
The difference between a madman and a saint is more often a thin line than a gaping chasm.
The difference between a hooker and a choir girl is often merely circumstance, or merely a slight twist in the genetic code.
Maybe 'Write what you know' should be 'Write what truths you know.'