Websites that are Just Text On A Page should load fast, but many don't. Hacker News is blazing fast, but Google's API docs never load.
The worst problem is that most UIs fail to account for slow requests. Buttons feel broken. Things that really shouldn't need megabytes of data to load still take minutes to load or just fail. Google Maps' entire UI is broken.
I wish that developers spent more time designing and testing for slow internet. Instead we get data hungry websites that only work great on fast company laptops with fast internet.
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On a related note, I run a website for a living, and moving to a static site generators was one of the best productivity moves I've made.
Instead of the latency of a CMS permeating everything I do, I edit text files at blazing speed, even when fully offline. I just push changes once I'm back online. It's a game changer.