You can use iOS’s built-in screen reader to narrate the Kindle app. I listened to an entire book that way. Audible is much better but you can do it this way too.
A colleague was saying to me that they would like to be able to have an ebook to read, but also to have it read out loud when driving or walking.
I think you need to set the Kindle app to continuous scrolling (in which case it won't work with older books), then you trigger the iOS screenreading shortcut, and off it goes.