A lot of the people who oppose this technique don't understand context: The right solution to your problem often involves understanding the problem you're trying to solve!

In my case, I work on two Blazor websites: One is standard in-browser WASM with Restful JSON (and some CSV) over http; the other is server-side Blazor that uses the websocket technique that this article describes.

The server-side Blazor approach is for an internal web application that has a lot of quick-and-dirty pages that replace what used to be ad-hoc database queries and ad-hoc scripts. It's not an "industrial strength" web application that requires high scalability, because it's only a handful of employees who use it. It's also a joy to work with. To be specific, we don't need to go through the exercise of designing an API, making sure that contracts serialize, ect, ect, just to slap a UI around what used to be a script.

The WASM page that uses Restful JSON (and csv) is our customer-facing web application: JSON (and CSV) help with debugging; but the cost of making an API is very high. Development on the customer-facing web site moves much more slowly, but it's "worth it" for an industrial-strength site.

Would I build a highly scalable website using HTML over a websocket? Maybe. The issue is time to market: Because you don't have to build an API, you can move faster; but I don't know if scalability issues will arise.