I'm someone who hasn't used Next.js a lot, and started building some projects with it (so I don't have a very nuanced opinion).

In general, I don't use the app router because I find it has little benefit as compared to the added complexity for my use cases (mvps / smaller projects). I've been bitten a couple times by not understanding the usage patterns and just making stuff "use client", so I just started using page router again.

I assume with more complex projects it helps, but I haven't experienced it first hand

It's okay to make things "use client" – it effectively functions like the Pages Router but with streaming support (so better performance without you needing to do anything, basically).

I'm currently building a project using App Router. Here are my thoughts so far:

1. In React Server Components, you fetch data at the component level instead of route level. You can pass the data down as props if it's a client component.

2. I'm not sure if HMR is faster in Pages, but in App Router it tends to be slow. I always use --turbo to see changes quickly, but it can still be a bit buggy.

3. I just found out that using "use client" directive isn't actually sending 100% javascript to the client. It's just a replacement of serverSideProps. The component is rendered both on the server and the client, which can be confusing at first. You can disable SSR using dynamic imports.

4. I actually like Route Groups, best feature by far.

Why is Next.js popular or useful? I realized after fighting with its complexity that I could have just done the whole thing in normal React.