There are framework concepts that chug along in the background and only occasionally surface like an iceberg (E.g. Trinity). Other theological concepts need to be constructed from a couple of sections (E.g. The nature of Scripture) and still other doctrines are common but always sit in the background (E.g. Relationships). Of course, some doctrines are laid out in clear sight (E.g. God's Judgement). Interestingly, some theological concepts rarely appear but nonetheless seem to have a qualitative weight beyond their quantity, I think Adam is one of them. (Another example is the presence and departure of God's glory in the temple.)
This isn't a problem theologically or apologetically. If every theological idea presented itself in equal proportion and in equal intensity we'd simply have white noise. The real trick is organizing their relative importance and relationship to each other.