We ran a PageSpeed test recently on a local competitor's own website, the kind of test any business owner can run for free on their own site in about thirty seconds. We're not naming who it was, because the point isn't to call anyone out. The point is that the results were such a clean, real world example of a pattern we see constantly that it was worth writing about.
What the test actually showed
On desktop, the site scored an 81 for performance, which is a reasonable, if not great, result. First Contentful Paint came in at 0.9 seconds, and the page felt fine to load.
On mobile, the same site scored a 47. Largest Contentful Paint, the metric that measures how long it takes for the main content on a page to actually become visible, came in at 15.0 seconds. Not 1.5. Fifteen full seconds. Google's own benchmark considers anything past about 2.5 seconds on mobile to already be poor. This site was roughly six times past that threshold.
Why the gap between desktop and mobile matters
A huge gap between a decent desktop score and a poor mobile score is one of the clearest fingerprints of a page builder heavy WordPress site. Desktop computers generally have more processing power and faster connections, so they can brute force their way through a bloated page without the problem being obvious. Mobile devices, especially on a slower connection, can't hide it. The extra plugin code, the page builder framework running underneath the content, and unoptimized images all pile up and hit hardest exactly where most of your visitors actually are, on their phones.
Why this actually matters for a business
Fifteen seconds is an eternity online. Most visitors on a slow connection will leave a page before it ever finishes loading, which means the business is losing potential customers before those customers ever see a single word about the business itself. On top of that, Google factors page speed directly into mobile search rankings, so a slow site isn't just losing visitors who already found it, it's also less likely to show up in search results in the first place. A slow mobile experience quietly costs a business twice.
Why this happens so often with WordPress
This isn't a knock on any individual developer's skill. It's a structural issue with how most WordPress sites, especially ones built with page builders like Divi or Elementor, are put together. Page builders load a large framework of code on every page to support drag and drop editing, whether or not that page actually needs it. Add in a handful of plugins for forms, sliders, or animations, and a mobile browser ends up downloading and processing a lot more than the page actually requires just to display some text and images.
A custom coded site doesn't carry that overhead. There's no page builder running in the background, no plugin framework loading code the page doesn't use, just the code that was actually written for that specific page.
Check your own site
You don't need to take our word for any of this. Google's PageSpeed Insights tool is free, and it takes less than a minute to run your own website through it. If your mobile score comes back significantly lower than your desktop score, that gap is worth paying attention to, because it's very likely costing you visitors and search visibility you don't even know you're missing.