Speed guidance tends to assume a marketing site with twelve pages and one hero image. Catalogue commerce is a different problem: the same template renders thousands of times, each with photography that shoppers are specifically there to look at.
The temptation is to compress imagery until the metrics pass. On a tile or jewellery catalogue that destroys the thing being sold. The work is elsewhere.
Start with what loads before anything visible. Third-party tags are usually the largest single cost on a commerce site, and most were added for a campaign that ended long ago. Audit them against a list of what each one is currently used for; anything without an owner comes out.
Then look at how images are actually requested. Correct sizing per breakpoint, modern formats with fallbacks, and genuine lazy-loading below the fold will normally do more than another round of compression — without touching perceived quality.
Finally, measure on the devices your customers use, on the connection they use, not on a desktop in the office. The gap between lab numbers and field data is where most of the disappointment lives.
More reading
Other notes.
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