I disagree with this. Very often, the bloat and bug-fix-but-not-really-cause-it's-now-unmaintainable creep ... that makes the application completely unworkable. I've taken applications that I could rework and I've taken applications
that were completely unfeasible to rework and that rewriting was a matter of 2-3 weeks, most of that reading the horrid application cause there were no requirements. (And, yes, it was large ... before I got my paws into it.) And, I got rid of unnecessary misfeatures and streamlined the code and migrated it from Tk to CGI and sped it up 5-fold.
So, don't say that rewriting is bad-horrible-evil-unclean. That's like saying "GOTO is bad in every instance". Wrong. It's bad in almost every instance. But, that's why they pay us the big bucks - to figure out that 1-100 instance where goto is not only not bad, but even suggested.
We are the carpenters and bricklayers of the Information Age.
Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.