So, it's really not a matter of 'leaving it up to the reader' so much as the author actually targeting a certain audience
I disagree a bit about "not a matter of leaving it up to the reader". Why? Because I earn my money with books on the other side of pole => by choosing and presenting literature in the adult section of my library.
And it's like dancing on egg shells: I try to interest readers for various kind of genres. So, those members relying on my judgement, I will find the appropriate entertainment for them, are dependent on me. I give them a short review about the content (using the magic key words, according to the reader type in front of me) and then leave it up to them if they enjoy a book or not. And maybe it's only my library members(but I know differently <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" /> ) => a lot of females love the Mary Sue kind of books. Can be as repetetive as you fear in your hardest nightmares - yes, they want these Mary Sues. And, writer, whoever you are => DON'T dare to walk astray and present them a different kind of typus <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" />
An example? Nora Roberts <shudder>, specially her new books, distorting the fantasy genre. Cartland, Woodiwiss ... name it and you hit the bull's eye. Trying to interest them for Doris Lessing, Carol Oates, Margaret Atwood? Nada - try to interest a Bradley fan into a different kind of fantasy? I'd make them unhappy.
I made the XP that readers are somewhat "conservative". They take a liking for one kind of genre and then stick to it - and it's not always about targeting them as a group.
So, I, the humble "literature broker", the book mule - I leave it up to the readers to decide.
Book plots have sadly become very repetetive as you described, Faralas. Maybe this is the cause why I mainly skim through books and put them only into my mobile RAM memory (brains) to pass on this knowledge. I have very very seldom found a novel in the last 5 years really interesting me up to the end. I'm talking as a reader now - and it's not only me: My colleagues and I have discussed this a few days ago => they feel the same. Nearly no innovation anymore. Sad, huh? <img src="/ubbthreads/images/graemlins/puppyeyes.gif" alt="" />