In any given month, the title chosen will undoubtedly have some people opting not to read it for any of many reasons. That's a given, and entirely valid. Issy isn't likely to read a Star Wars book -- I get that.
What we're discussing here is how to make sure that we keep obvious blocking factors in mind when we make our selections. Both in the nominating process, and especially in the final voting process. And what several of us are suggesting is that long books (>500 pages or so), are more likely to cause people to opt out that month. As would, for example, a book not readily available from the US, or a book priced at $15 or more. (Even $9.99 is a lot for some people, and can be a blocker if the book isn't readily available from their library.)