I work in ecommerce and I feel it’s somewhere in between. We need to build for seo optimizations for the category/product experiences yet there is a lot of application like intersections, especially on the category filtering and the product sku selections. Quickshops, In store pickup modals, user specific recommendations trays, add and edit reviews et all. Different caching for server render at the edge vs personalized components adds another layer. Being able to serve with a shared routing scheme both client side (for improved performance) and server side for faster initial page load and seo on non-Google crawlers is a tough problem. Especially when you add in client hydration of the redux store. That parse time is a real killer on mobile. You add in service workers and prefetching and the complexity ratchets up further. The other issue we deal with is marketing pixels and trackers. But that’s another story. There is a ton of complexity in building a highly functioning ecommerce site.