People forget how bad MPAs were, and how expensive/complicated they were to run.
Front end frameworks like svelte let you write nearly pure HTML and JS, and then the backend just supplies data.
Having the backend write HTML seems bonkers to me, instead of writing HTML on the client and debugging it, you get to write code that writes code that you then get to debug. Lovely!
Even more complex frameworks, like React, you have tools like JSX that map pretty directly to HTML, and in my experience a lot of the hard to debug problems come up with the framework tries to get smart and doesn't just stupidly pop out HTML.