Rewriting a whole system from scratch is almost always a bad idea. Rewriting a system part by part is much more achievable with each part going into production

Rewriting a whole system from scratch is almost always a bad idea. Rewriting a system part by part is much more achievable with each part going into production incrementally. In the end you might have a 100% rewrite, but doing it incrementally keeps the system sane. Doing this way also often ends in failure though because it takes longer and often the rewrite stops midway (business requirements change, key person leaves, organisation rework) and now you have two competing architectures in your product.