I think JS does play a big role, but my guess is that the 3rd party stuff is lots heavier than the scripts that actually make the page work. You have to write t

I think JS does play a big role, but my guess is that the 3rd party stuff is lots heavier than the scripts that actually make the page work. You have to write tons of code before the load time even matters, but when you have a bunch of "analytics", advertising, and social media integration scripts it adds up, especially when each ad is essentially it's own page with images and scripts. If you use Privacy Badger or similar plugins, you see that it's not uncommon for websites to have an obscene amount of these. TLDR: I think ads are slowing the internet down way more than React apps.