While I haven't personally used it, Compose for Web basically replaces Vue/React/Angular for the task of applying data to HTML. But you'll still need to know HTML/CSS to make a web app with it, just like with those other frameworks.
Unfortunately, for the time-being, Compose just modifies normal browser DOM and doesn't use the Material UI (though I believe there is a long-term roadmap to support Skia and use Material UI like with Desktop), but I don't think you'd need to know much JS to work with Compose Web, just HTML/CSS.
However, there are KMP libraries for most of the typical browser APIs you'd normally need (API clients, key-value storage, and routing, for example), so you don't have to drop down into that untyped hellscape called the JS Standard Library.