NYT site is fast, but is broke as hell. Even turning off uBlock it downloads 10mb of assets before the fold and still doesn't work.
This is more salt of the earth reality, maybe you're projecting the snooty nose-in-the-air boutique'ness of React.
I generally agree that most sites are pretty bad, are way too big & usually with poor data-architectures (over fetching, re fetching, poor or no data caching). Data storage is notably something React nor very few other things have tried to tackle. GraphQL made a forray & for a while seemed ascendant but it's moment seems to be passing. The core issue of client-server model is still pretty informally handled.
But even that has nothing to do with the very obvious & bad issue, that many sites are loaded with obnoxious & heavyweight & surveiling ad payloads. But it's unclear to me again what React has to do with this. (Especially as few of these as systems use React.)