Do you know of good SPAs? Sites that feel snappy even though they're SPAs. Most sites I visit that are SPAs are consistently slow so I've learned to make the same association: SPA = bad.
The simple question as to where are all these inspiring SPAs that truly push the web to next levels...is completely unanswered.
We get docs sites, demos and blogs. Where when clicking on a link...wow!...it loads without a page refresh. Something possible using simple ajax some 15 years ago.
Do you investigate all the fast snappy sites you visit to confirm they aren't single page apps? What about the slow pages that aren't SPAs (most every news site)?
It seems like anyone who wants to dislike JS and/or SPAs can easily confirmation-bias their way into believing it.
Anyway, for fast SPAs, here is a useful comparison: the "RealWorld app" demo.
I would urge everyone to look at the Lighthouse audits for these three implementations:
React/Redux: https://react-redux.realworld.io/
Angular: https://angular.realworld.io/
Vue: https://vue-vuex-realworld.netlify.app/#/
Svelte/Sapper: https://realworld.svelte.dev/
Solid.js: https://ryansolid.github.io/solid-realworld/
This is just a demo, of course, but it is close enough to be representative. From just this simple demo we can already see significant differences: Svelte and Solid.js are much snappier. The author of the article, Rich, created Svelte.
Of course, this is just talking about performance, not yet getting accessibility, navigation, transitions, etc right.