I wouldn't say it's stable or dead. Starlette and FastAPI are great async frameworks that seem to have replaced Tornado. Django is only recently getting some async support.

JS frontend seems to have been going through churn for over a decade now. It's a messy language, and because we've been forced to use it as the sole frontend language for a while people have been trying to figure out how best develop with it. Hopefully, with more language support in Wasm, JS will finally be replaced.