> Sure, but my point is, if the code is not well designed, the result of a ground-up rewrite will not be well-design either,
That doesn't follow for me, sorry.
A rewrite, as I understand and use the term, doesn't mean transpiling what exist to, say another language or to another framework. The old version is essentially just a very detailed and testable list of functional requirements; everything the old thing can do (as long as that functionality is still actually useful), the new thing must be able to do as well.
How this functionality is implemented in the rewritten version, and how it's internals are designed, is entirely up to the rebuild. The way functionality is implemented in the predecessor does not necessarily determine how it is implemented in the new version.
