Do you actually write software for money?
Most commercial software is never designed, it evolves, over the course of repeated "agile" "sprints". Every two weeks, someone hacks together something that kinda-sorta works and then that is released.
Eventually (often many years later) the thing becomes so complex and unwieldy that it's impossible to add any more features, so someone gets angry, throws it away, and starts again growing a new monster.