When you have a team with predominantly back-end knowledge expertise using a templating language they are familiar with plays to their strengths. MVC applications were written for over a decade. Perhaps it is a subjective thing because I don't see any logical difficulty in a web page that exchanges partials instead of JSON. I was programming that way for over 10 years.
Svelte really sounds compelling from what you're telling me. I'll check it out. But unless it is a drastic simplification it brings with it the fundamentals of effectively writing a thick client in JavaScript or TypeScript and all the things that come with it. React and angular have left a very bad taste in my mouth. The time and code cost for building basic user interfaces should go down not up. We should be spending less time talking about how to do something and more time talking about what to do
95% of what you write in Svelte is just HTML. You then databind whatever you need using an obscenely lightweight syntax.
Svelte also has an optional SRS framework called SvelteKit that auto creates REST endpoints for you, and auto binds stuff to them, but all that is optional and not needed.
My issue with backend HTML templates is that essentially you always have to know HTML + CSS anyway because browsers suck and they still have differences, so I always end up spending a ton of time fixing CSS and HTML issues. Having to fix HTML issues by way of the backend that then generates HTML feels like an unneeded abstraction.
React is boilerplate madness.
Do the same in Svelte.
I did a form heavy app in Svelte, literally took 1/5th the time it would have taken in React.
SPA fundamentally means that instead of refreshing the page, just the data needed to update what is on screen is sent down to the user.
Ideally, "send data about products on next page of search results" is less than "send all HTML needed to render the next page of search results."
Also the backend ends up simpler, instead of trying to template strings together, the code can just worry about fetching and returning needed data.
I am legit confused why people think generating HTML in some other language (Python, Ruby, etc) is a good idea.
Keep HTML in the browser (easier to develop and debug!) and keep backend business logic someplace else.