In my opinion SPAs are simply a progressive enhancement for MPAs which allow even faster page navigation.

While I agree that there is a spectrum (hinting at that with the last paragraph), this is where I hard disagree. To construct something like this, you are making an application massively complex by trying to re-implement everything on both ends. Using something like Astro is only hiding that complexity but it’s still there, & probably full of bugs & tons of JavaScript that most developers wouldn’t even understand their stack or know how to jump into the Astro code. The amount of time saved is largely minuscule in most cases with the assets cached when navigating to a new page. In fact, I just tested two of their showcased sites which loaded slower with JavaScript enabled & the content was pretty obviously 95% static. There’s probably some niche use cases for this, but it’s not a good default IMO.