KweekTechA site built and signed off on a recent laptop over fibre gives a completely misleading impression of speed. In most emerging markets the majority of traffic arrives on a phone, often on a metered plan and a handset several years old. Those are different physics.
The first culprit is almost always the image. A photo straight off a phone weighs several megabytes; resized correctly and converted to a modern format it frequently drops below a hundred kilobytes with no visible difference. The ratio is measured in tens of times, not in percentages — and it is the cheapest fix available.
The second is accumulated libraries. Every script added must be downloaded, parsed and executed before the page responds. On a modest device it is the execution, not the download, that costs most. A page that is light over fibre can still be unusable on a four-year-old Android, because the bottleneck moved from the network to the processor.
The third is client-only rendering. A page that shows nothing until JavaScript has finished executing leaves the visitor in front of a white screen and deprives search engines of content to index. For a marketing site that is not a trade-off, it is a defect — and it is the single most common reason a well-built site produces no enquiries.
The practical test costs nothing: open your own site on a mid-range phone, on mobile data, away from your office wifi. Most people who do this once never argue about performance budgets again.