I strongly disagree with this. SPA has its place and a very important one. It is not just about replacing JS animations with CSS animations. Of course it depends on the use case - SPA makes little sense in many cases and a lot of sense in few. But it still has it's stable place.

From my own point of view and experience, SPA makes the most sense when you do not want to bundle backend and frontend together in your server code. Having a separate FE and BE with clearly set API(json) is very important in many many many cases and it allows you to use the same BE for different FE, like desktop website, mobile website, desktop client(electron), mobile application... trying to do this on the server would be hell. Also worth mentioning is that if you want to make changes in your FE, you have to bring down you BE in order to deploy them, whereas if you have BE and FE separated, you can deploy the FE without any downtime.

There is a lot more that could be said but the main point is that moving data rendering into FE and letting BE just serve raw data is the way to go in many situations.

We have been moving computation between FE and BE for decades now, but I think the tech is now sufficient to not force us to pick one over the other but chose what works best.

Personally, I think that rendering the UI on BE is archaic and should be handled on the client via some bundled thin client code, ala SPA. So I will always prefer client-rendering over server-rendering, no matter the setup.

PS: You might be interested in https://data-star.dev/ which came out of dissatistfaction with HTMX and I think will be the way to go about bridging FE and BE in the future.