I can. Even if you design a good system up front, the requirements graph changes over time until your great ideas have turned into hindrances. This can be scali

I can. Even if you design a good system up front, the requirements graph changes over time until your great ideas have turned into hindrances. This can be scaling issues, but mostly it's where reality turned out to be different than your abstractions were built for. Maybe you made one module very generic but now it's cumbersome to add features to. Maybe you didn't add enough flexibility in another place which resulted in a buildup of suboptimal code. Maybe extreme concurrency was planned for but never needed and now the person has left and no one else understands how that part of the system works. So now, over time, this emergent phenomenon that some call code rot causes your beautiful, elegant greenfield project to turn into a monster that no one wants to touch. It's hard to modify, easy to break, and takes forever to work on. It's legacy code.