EDIT: Also the concept of "virtual DOM" is way older than shitty websites themselves (was applied to native GUI stuff before JS was even a thing). What you're seeing is just a shitty website.
Yeah. It’s not like functional programming is known for being slow, and every page adopting these ridiculous strategies has universally gotten worse and slower. Oh wait.
That's not how virtual DOM works.
EDIT: Also the concept of "virtual DOM" is way older than shitty websites themselves (was applied to native GUI stuff before JS was even a thing). What you're seeing is just a shitty website.