Challenging the cutting edge of your product domain is what I get from this. Easy things are easy and predictable. Hard things and unpredictable evolving requirements are a tension against the initial system design which is the foundation of your code base. Over time the larger projects get the perhaps further they deviate from the original design. If you could predict it up front in many cases its not all that interesting or challenging of a problem. Duct tape is fine to use as long as you understand when you've gone too far and might want to re-design from scratch based on prior learnings.