I saw this earlier today (Edit: instead of the first 10 minutes, I ended up watching the whole thing.) After going into the problems of client side rendering, he does get into the benefits (9:00), but then argues that these are after-the-fact rationalizations. He then argues that the real problem designers and devs are trying to solve is the loss of control - that the browser controls loading, and the blank screen is "bad."

He then says that the solution is using an iframe (called a portal.) which looks to be a proposed API. https://web.dev/hands-on-portals/ - this is available as an origin trial in Chrome 85.

So, he's saying that SPAs are bad and we should invest in a Chrome-only feature or future feature that might make it through standards? This makes no sense to me.

There are multiple uses for SPAs. One is building a genuine web application, such as Gmail or a SAAS. SPAs are also used in places they shouldn't, such as news sites, because of the page load problem as mentioned above. Portals would be useful here.

But it gets to the real problem: client side rendering in the past decade has had a lot more thought and effort in tooling, tutorials, and patterns on the client side than server side, especially with mixed mode. (Mixed mode: adding javascript on top of server-side rendering.) The problem is that server-side rendering and mixed mode is not a good development experience. The back button was never a fully solved problem and POST-redirect-GET is essentially an insufficient hack.

If someone wants to talk about making server side rendering for web applications a viable experience, we are likely going to need changes to the standards and we will need to build up a great set of tooling to solve the problem. (Oh, and since it's server-side rather than javascript, each framework or language will have to replicate it just like React, Angular, Vue, and others have done.)