I'm talking about tech like LiveView, Hotwire, LiveWire, Blazor, etc. They use JS (in some cases with websockets) behind the scenes to send small bits of html which are patched into the DOM. The win here is that you can write all your business logic on the server and don't need an intermediary API for your frontapp to talk to your backend app, you just send HTML.

If you're building an where you are going to open up an API, there is a little less benefit, but I've worked on projects in recent years where the API exists solely to be consumed by one client.