Reader development takes an inclusive approach to whatever people are reading. We don’t need to make value judgments about the 'quality' of books as we shift the focus to the quality of the reading experience. It is quite possible to have a poor reading experience with a great book - most of us have experienced this at school or later in life. This doesn't mean that generations of readers have been wrong about the book and you're the first person to see through it. Nor does it mean that there is something wrong with you or that you are simply not up to it. All it means is that you and the book weren't right for each other at that time, something prevented the book from speaking to you.
Conversely, it is possible to have a deep and satisfying reading experience with a book which is actually quite light, which may not be a book of all time, but which just happens to speak to you at a particular point in your life.
Each reader is the judge of their own best book. Reader development will always seek to encourage people to try something different or new to them - but the final judgment on whether it was worth it is down to the individual reader. Everyone is expert in their own reading experience.