Why was it considered a bad move to go SPA? I generally disagree with this statement. But I feel like whenever this conversation comes up we're talking different applications altogether. A SPA is fine for a back office application. What it's not necessarily good for is a splash page or marketing page where each page truly operates independently. But in the case of an app that people use frequently, the client side code all gets cached locally anyways, and SSR doesn't buy you anything for that use case. SSR is great for getting a fast time to render on the very first hit to a page. But if you're making a real, rich app, that people will use daily client side JS is not bad at all.
I worked on Trello for a while, it was a single page app with a Node.js API. We served millions of users with it, and people generally loved the UX of our app. But it was a true web app, and not a website. Interactivity was always part of the user experience, and many of the behaviors would be impossible in a pure SSR app.