Non-SPA feels slow. It doesn't matter that much if it's slower or not, because the perception is slow. If I'm on a page, click on something, and in the background it loads some new content and updates part of (or even the entire) page, at least while I'm waiting, there's usually something else to read or potentially interact with in some way. Maybe there's a spinner for requests over ~200ms. It feels like the app is doing some work but it otherwise present. If every click results in a new page render, my browser immediately clears the page and I'm left looking at a blank page waiting for content to render. Even if that somehow takes half the time, it feels like an eternity, and there's nothing for me to look at while I wait. And that full-page redraw is visually distracting.