Largest Contentful Paint measures how fast the main content appears. Interaction to Next Paint (which replaced First Input Delay) measures how responsive the page feels once someone actually tries to use it. Cumulative Layout Shift measures how much the page jumps around while loading. All three still feed into Google's ranking systems.
Once a site passes the thresholds, nobody revisits it — until a new hero carousel, a third embedded chat widget, or an unoptimized video gets added six months later and nobody notices the regression because nobody's watching the dashboard anymore.
A slow product page doesn't just rank worse — it directly suppresses the exact page meant to convert. Checking Core Web Vitals on your top 20 product pages quarterly catches regressions before they compound into both a ranking problem and a revenue problem simultaneously.