In the hundreds of websites I’ve designed and built, I’ve learned that there’s only a few common issues that warrant a redesign.
Of those, the two biggest are having a poor user experience and interface, and having a site that’s slow to load.
With the former, this affects what happens when a visitor is on your site, and they likely to leave the site without contacting you. With the latter, it’ll be a wonder if visitors even get to your site, as Google ranks faster sites higher in search.