ALT Hacker News comment: I think you're talking past each other: the problem isn't assuming the client's internet is fast, the problem is assuming the client's internet is stable. If you replace most interactions that could be resolved client-side with a network transaction, you're betting on the client's internet being not just reasonably fast but also very stable. When I'm on the go, my internet is more likely to be fast than stable.

ALT Hacker News comment: For a real world example of this, GitHub uses server-side rendered fragments. Working with low latency and fast internet in the office, the experience is excellent. Trying to do the same outside with mobile internet, and even with a 5G connection, the increased latency makes the application frustrating to use. Every click is delayed, even for simple actions like opening menus on comments, filtering files or expanding collapsed code sections. I'm actually worried about developers in developing countries where mobile internet is the dominant way to access the Internet and GitHub is now the de facto way to participate in open source, that this is creating an invisible barrier to access.