[yawaworht1978]

Some of the scripts need to be placed in the head section of the document which is a blocking operation.

Some of the ads are generated on the run based on that tracking data and it involves many, many http round-trips before it's injected via ajax. Further, comment sections have some sort of fb tracking integration, triggering even more round trips.

And all that is separately loaded on a non optimized website layer with many externa JavaScript frameworks and dependencies.As well as injected video components, huge images which most likely aren't optimized. Lazy loading should be native now, no jQuery function needed, no intersection observer either, and it does work ok, but it's often not properly implemented or not at all.

As for react, the stripped shadow Dom might be faster then the native Dom, but you still need the Dom and react is still a heavy load. I remember the days when people said don't needlessly load jQuery. Today, people use react when there's no real need to do so.