What’s so special about Jamstack serverless vs full stack monolithic application?

I’ve seen couple of tutorials and doc about how Jamstack work and to be honest, it isn’t so much easier compared to monolithic driven app. I was interested in learning it because I’ve heard it’s easier and more performant. But like I’ve said the difficulty isn’t that different compared to classical server side rendered design. In front end part you need to make a function folder to connect to the api, you still need a backend and database to call to. So I don’t understand what’s the big deal of it? I’m still not convinced to switch from MERN stack or Laravel deploying to Heroku and its database to Postgres than Nuxt or React deploying to Netlify, using Lambda functions and still using backend side somewhere else or Firebase.