> One mistake I've seen a lot is assuming that an extensive code base, developed by competent engineers, but which is very complex needs simplifying or rewritin

> One mistake I've seen a lot is assuming that an extensive code base, developed by competent engineers, but which is very complex needs simplifying or rewriting in a simpler way. Omg, this yes. I've made this mistake countless times. I'e done my share of rewrites or refactorings that ended poorly. Work long enough on a big project, and junior engineers will do it to your code too. Being on that end of it is a very frustrating experience. But let's now balance that against the assumption at the other end of the spectrum: that an extensive code base, developed by competent engineers doesn't need simplifying or rewriting in a simpler way. As it turns out, this too, is a flawed assumption. The more code I've seen, the more I've seen that most codebases that have survived any length of time are a mix of both, and it's hard to figure out what is what until you get some deep experience with it yourself. If there's been turnover in the team and the code has been under heavy churn, it's probably a mix of everything!