Did you try it? Try with 256Kb/s and 20% packet loss (and if your networking tooling allows it, bursts of >1s downtime every 20s) and tell me which one performs better. Yes that's actual conditions in which many people access the Internet in 2021 whether it's on cellular or crappy xDSL.
I've yet to see a single SPA that can deal with such conditions, while native HTML/CSS will work like a breeze in any web browser. For bonus points, browser UI can tell you which requests take a long time and/or refresh any page while maintaining a cache, something most SPAs are really bad at doing, and you get SEO/interoperability for free due to your markup being a curl call away from any client.