Most of the web really sucks on fast internet connections too. Thanks to so many web developers thinking every dang thing needs to be a single page app using a heavy JavaScript framework. Add animation, badly optimized images and of course ads and it becomes really unbearable.
We keep repeating our same mistakes but just in a different way.
I saw a sarcastic comment a while back saying that webdevs should be forced to work on a Pentium II machine and they would cut their bullshit, I laughed, and moved on.
But after seeing many examples where sites were built on huge iMacs with no care for users running off a battery, slower network connection or with an average 1366x768 display I somewhat agree with the sentiment.
I tend to run web frontends in lynx (or links) to see if they can degrade well enough. If the core user flows don't/can't work then there's a big problem with the UI.
We keep repeating our same mistakes but just in a different way.