The reason behind this wisdom is that it's easy to suggest a rewrite because you think the current code is too complex. You suggest a rewrite because you cannot

The reason behind this wisdom is that it's easy to suggest a rewrite because you think the current code is too complex. You suggest a rewrite because you cannot grasp the current code. If that's the case, then I think the mentioned wisdom more or less holds up. However, it's also possible to understand the complexities of the current code, and still suggest a rewrite. Then the likelihood of a success is much, much bigger, I think. I'm not 100% sure, but I'm under the impression that imdb.com pulled off such a rewrite a couple of years ago.