Your content may be good, but if it is the same content as it was 5 years ago, then search engines may no longer think it is relevant, so it is very likely to drop in search engine rankings. Redesign also gives you the opportunity to rethink your keyword targeting and overall conversion rate of your site, because the way people search has changed dramatically in recent years.
An old website may not be equipped with the necessary tools to help you measure how effective your online presence is. Examples of this are conversion tracking and user registrations. Today, there are a variety of online tools you can invest in to help you measure what works and what does not on your site down to the smallest detail. However, to use them, you will need a modern website.
An important factor to consider is the increase in usability in web design. Every year the web standards change radically and the techniques for building websites become more advanced in order to comply with the latest standards. If your site was developed several years ago, it probably has a lot of unnecessary HTML code and can slow down your site’s loading speeds – which in turn can affect your ranking in Google search results.