I inherited a piece of code that was designed as a state machine and the state machine design basically made the project become pure technical debt as requirements increased over time and engineers had to make it work with the state machine model that had been chosen when the project started.

If the project had instead been designed to have less unnecessary state and “transitions” it would have been a lot easier to make changes.

All those ideas sound good by themselves but they are really bad for “defensive” coding. Good luck selling a project to refactor something when it’s going to take multiple people-years. Once you’ve made the mistake of committing to an inflexible design it’s either that, replace/ignore the thing, or deal with low productivity as long as the thing exists.