I watched the Jamstack talk and I dont think Rich quite grasp why some people are against SPA.
The first thing being, 95% of what I do on the web doesn't need to be an SPA. Most of what I do is content consumption. HN doesn't need to be SPA. NewsReading doesn't need to be an SPA.
The second thing being once you allowed developers of SPA, and break free of the browser default usage pattern, there are very few SPA I have used that I even considered to be decent. Actually there is only one, Feedly. And yes, as pointed out in the video, even instagram cant do the basic right. Not Facebook web, and not Twitter. Look at new Reddit.
The problem with SPA is once you try to make a Web App, aka Reddit, I will instantly try to compare it with a Native App. And I have yet to see a single decent Web App that compares to "average" native app. It is far easier to make a very decent MPA with added magic like HTMX or Hotwire than a decent SPA.
The third being transitional design. Which is a compromise or taking best of both worlds. Interestingly HTMX or Hotwire are also considered as Transitional, since they try to make the those web page that needs a little more interactively without switching to SPA.
There are some things that are better for SPA, so far most them for me tends to be financial tools and graph based.
One argument for SPA is that your backend is just an API, your front end could now work not only in browser but even compiled natively into Apps. But so far none of them worked flawlessly across all platform without a team of expert.
And for simplicity, PHP is still by far the best in modern web backend tool kit. I am not advocating for PHP, I hate the syntax but other than that it is dead simple to use and set up. Considering both Hotwire / HTMX with Django and SPA camp with Svelte just shows how little the vocal web developer community value simplicity.