Former frontend performance guy here – "Cumulative Layout Shift" is the measure of this jank, and yes, it is the absolute worst.

Conversely, it's hard to overstate how magical sites become when you get that down to 0. Once stuff stops shifting, users are effectively fooled into believing that sites are finished loading. Sites just feel fast, even if things are still happening. It's sadly hard to get there, and very easily worsens.

Yeah I love when I click a thing then a different think appears under it 0.5ms before click registers.

> Why is this still a thing?

HTML/CSS/JS stack makes that the default and coding your way out of that is hard

Hilariously, I was trying to enable the minimal JS needed to view that page, and UMatrix DID THE EXACT SAME THING, it shifted down a site I wanted to block under my mouse button. :)

For all you dystopian fiction writers:

the end of all humanity, caused by lazy loading JavaScript.

It shouldn't take more than a weekend, and the "Terrifyingly realistic!" reviews will write themselves.

I suspect the real reason it's still a thing is that it makes users more likely to click on ads, which is after all how most of the internet makes its money.