But what if your dependency graph never becomes large (HN, Craiglist,...)?

I believe a lot of web applications can go without any reactive framework as using one is a slippery slope. You start with React and 80% of your code is replacing browser features. Imperative may not be as elegant, but it simpler when you don't need that much extra interactivity.

Then you don't need it. Same for if you can do everything (or most everything) with page reloads, or if you don't have any reactivity at all. But the problem is still real, even if people use frameworks when they don't really have to.