I have designed and built something that could be described as a microfrontend system (though it's much more restrictive than "do what you like within this part

I have designed and built something that could be described as a microfrontend system (though it's much more restrictive than "do what you like within this part of the page") and though it's been pretty successful I agree totally with the article. It's a lot of complexity if it isn't definitely worth it. Our "microfrontends" are really dynamically-loaded JavaScript modules of a particular type. They conform to one of a small handful of well-defined extension points, including defining UI (in React components, as it happens, but clearly this isn't React-specific). In this way engineers stay more or less on the golden path, and we can do some runtime checks to try and give better error messages. I think if we'd built something more general it would have been a mistake.