I often find myself in this situation too :( I try to get over it by purposefully buying books based on the synopsis, that I've never heard of, or which aren't discussed in mainstream circles - if only to preserve that sense of mystery, as you say. I'm not saying it's easy, especially with the whole need-to-check-off-the-mental-tbr thing, but it often works! I've found many books which I genuinely enjoy and love that way