Infinite scroll launched in 2006. Perfect for users. Catastrophic for crawlers.
Googlebot lands on your page, indexes what's visible, and leaves. Everything below the fold that loads on scroll? Doesn't exist. Martin Splitt finally admitted it in 2020: "Googlebot doesn't scroll." One developer discovered their entire content library was invisible to search engines beyond the navigation menu.
The operational reality: you now maintain two content delivery systems. Infinite scroll for humans. Paginated URLs for bots. A UX decision from fifteen years ago means permanent infrastructure overhead because nobody asked how crawlers actually work.