Avoid one-cause thinking
A fast builder on a badly configured stack can be slow; a feature-rich builder on a disciplined stack can perform well.
Measure real pages
Use representative pages, not empty demos. Test Core Web Vitals, transfer size, requests and interaction behavior after adding the plugins and media you actually use.
Control design excess
Nested layouts, animation, video backgrounds, multiple font families and third-party widgets can hurt performance regardless of builder.
Divi 5 context
Elegant Themes has emphasized performance and architecture changes throughout Divi 5 development, but production performance should still be measured on your specific site.