It's not either or. There are best practices that can be followed regardless with no time cost up front, and there is taking some time to think about how your product might evolve (which you really should be doing anyhow) then making choices with your software that don't make the evolution process harder than it needs to be.

Layers of abstraction make code harder to reason about and work with, so it's a lose lose when trying to iterate quickly, but there's also the idea of architectural "mise en place" vs "just dump shit where it's most convenient right now and don't worry about later" which will result near immediate productivity losses due to system incoherence and disorganization.