Going from "not written to be easily maintainable" to "unmaintainable" is exactly the problem you see very often. Instead of investing a bit of time to learn things and make them incrementally better people cry foul when it's not perfectly to their liking (i.e. if they haven't written it themself) and tell you later when you ask them if that monstrosity they've written was really necessary - which probably doesn't work and/or has bugs which had been already fixed in the original codebase - that it was "unmaintanable" and so they "had" to rewrite it.
Going from "not written to be easily maintainable" to "unmaintainable" is exactly the problem you see very often. Instead of investing a bit of time to learn things and make them incrementally better people cry foul when it's not perfectly to their liking (i.e. if they haven't written it themself) and tell you later when you ask them if that monstrosity they've written was really necessary - which probably doesn't work and/or has bugs which had been already fixed in the original codebase - that it was "unmaintanable" and so they "had" to rewrite it.