This, this, this. Users didn’t ask for magazine websites - which should be serving up, y’know, images and text - to sit and spin on my phone while all the Javascript libraries load. Users didn’t ask for these things; we as a community just decided to foist it on them.
A lot of the slowest stuff on websites are trackers that are being foist on developers to foist on the users (if the developers even have control over the trackers, like with GTM)
