Which is remarkable given how many older systems and software the pi can run natively or emulate at full speed. The web really can be embarassing in terms of performance.
It is awful, isn't it? I do wonder how many joules we waste on poorly performing web apps that could be made more efficient by applying less engineering rather than more.
As a javascript dev myself which write javascript heavy websites, I think all of my sites would perform just fine on a raspberry pi, at least on the newer models.
What I am most afraid of is the editing experience mostly.