The challenge for us as writers then is to ensure our own characters and themes resonate so readers will want to engage with them. How can we do this? By ensuring that our characters have virtues we aspire to and failures we can sympathise with! No goody-goodies. No villains who act in ways we can't understand. There has to be a reason for them acting the way they are, even if the reason isn't a good one. A reader has to be able to see where the character is coming from even if they think (rightly or wrongly) the character is going in totally the wrong direction!
As for themes, you can't beat the big ones of love, justice, redemption etc. What matters is the take we bring to these themes. My voice (and therefore my characters) will be unique to me, yours will be unique to you. Mix things up. Often the themes of love and redemption are used together and very powerfully too. So write about what matters to you. If justice is your raison d'etre, then how can you convey that in a story? Do you have a character who fights passionately for justice or who has been a victim of injustice? What makes your character special that they're going to stand out to, firstly, an editor and, secondly, readers?
Work out what you would like your story to convey. Planning is vital, I find, to stop me going off at a tangent. Focus. Edit. Fine tune your story so you ensure it meets your theme. Cut out anything that doesn't help the story with that objective. And have fun doing it!