This 25-year-old article by Joel Spolsky, about how doing a complete rewrite of Netscape killed it, is still one of the most important articles ever posted on the Internet:
Things You Should Never Do, Part I
Netscape 6.0 is finally going into its first public beta. There never was a version 5.0. The last major release, version 4.0, was released almost three years ago. Three years is an awfully long tim…
www.joelonsoftware.com
BTW, in the mainframe world, all the folks who are advocating rewriting millions of lines of old COBOL code in Java are facing the same issue.