The key to improving website performance lies in identifying and fixing render-blocking resources, which are JavaScript and CSS files that prevent the web page from loading until they are downloaded. By using tools like Chrome DevTools and Sentry, developers can identify these resources and optimize their load times, leading to improved user experience, increased ad revenue, and better search engine rankings. Inlining critical CSS, removing unused CSS, conditionally rendering media queries, deferring non-critical JavaScript, and minifying CSS and JavaScript files are effective ways to improve website performance. Additionally, monitoring web vitals in production with tools like Sentry helps ensure a good user experience without manual monitoring, making it easier to identify areas for improvement and optimize the website's performance.