As far as premature optimizations, if they're truly premature and moderate/high effort then yea, you're usually better off getting things working quickly first. But I've seen the admonishment of premature optimization often used to turn a blind eye on the technical debt that can result from simply going fast. Successful projects require doing the simplest thing possible that will work while maintaining a conscious effort to keep track of refactoring candidates, performance inefficiencies and other messes that'd otherwise languish under the rug and, maybe, just improving them before proceeding.