Aim for the main content visible inside ~2.5 seconds on a phone. That's the threshold Google's own Core Web Vitals ('Largest Contentful Paint') defines as good, and it's where visitor patience measurably runs out.
Speed compounds quietly: it's a ranking input, a Quality Score input for ads, and a conversion input all at once. The usual culprits are oversized images, tag bloat, and cheap hosting. Boring fixes, big returns.
Test with Google's free PageSpeed Insights on your top pages (not just the homepage), on mobile, and fix the largest flagged item first rather than chasing a perfect score. Past 'good', speed work hits diminishing returns fast.