The Largest Contentful Paint (LCP) metric measures the time it takes for the largest visible element, usually the main product image on a product page, to fully render. When that image is marked loading="lazy", the browser deliberately delays its download until it detects the element is about to enter the viewport, which is exactly the opposite of what you want for an element already visible on load.
The fix is not a plugin setting but an HTML attribute on the theme template : remove loading="lazy" from the main product image and add fetchpriority="high" instead, which tells the browser to fetch that specific resource before others of similar priority. Chrome DevTools' Performance panel and Lighthouse both flag the LCP element directly in their report, so you do not have to guess which image is being measured.
ImagePipe already reduces the transfer weight of that image through the product_page preset : format negotiation picks AVIF or WebP automatically based on the browser's Accept header, and the preset's dimensions match the actual display size instead of shipping an oversized original. None of that changes how the browser schedules the download, though : priority and lazy-loading are theme-level markup decisions, independent from the image bytes ImagePipe serves.
Check first which element PageSpeed Insights or Lighthouse actually reports as LCP, since it is not always the product image on every template. Check next, in the Network tab, whether that image request starts early in the waterfall or waits behind other resources. Finally, open the theme's product template and confirm the img tag carries fetchpriority="high" and no loading="lazy" attribute.