Aren't WASM Components pretty constrained? My (very fuzzy) understanding is that they must basically manage all of their own memory, and they can only interact by passing around integer handles corresponding to objects they manage internally.

Part of the component model is codegen to build object structures in each language so that you can pass by reference objects that have an agreed upon shape.

Yes they each have their own linear memory, that’s one of the advantages of component model. It provides isolation at the library level and you don’t have to implicitly agree that each library gets the level of access your application does. It provides security against supply chain side attacks.

Having said that, component model isn’t supported by all runtimes and since its binding and code gen are static at compile time, it’s not useful for every situation. Think of it like a C FFI more than a web API receiving JSON, for example. Upgrading the library version would mean upgrading your bindings and rebuilding your app binary too, the two must move in lock-step.