I think it's circumstantial - do your abstractions make it easier or harder to implement and integrate the sort of features that the application generally requi

I think it's circumstantial - do your abstractions make it easier or harder to implement and integrate the sort of features that the application generally requires? There's sometimes significant use in having some powerful abstractions in place to allow for code reuse and application customisation - but all too often people build fortresses of functionality with no idea how or if it's ever going to be used. Foresight is useful here; if you can look at new features and break them up into feature specific business logic and generalisable application logic, then similar features can be cleanly integrated with less work in the future. Sometimes however, the level of customisability far exceeds what is strictly necessary; the complexities involved no longer help, but rather hinder - not only understanding, but feature implementation and integration as well.