JVM Green Threads here serve predominantly back-end scenarios, where most of the items on the list are not of concern. This list also exists to address bad habits that carried over from before the tasks were introduced, many years ago.

In general, the perceived want of green threads is in part caused by misunderstanding of that one bad article about function coloring. And that one bad article about function coloring also does not talk about the way you do async in C#.

Async/await in C# in back-end is a very easy to work with model with explicit understanding where a method returns an operation that promises to complete in the future or not, and composing tasks[0] for easy (massive) concurrency is significantly more idiomatic than doing so with green threads or completable futures that existed in Java before these. And as evidenced by adoption of green threads by large scale Java projects, turns out the failure modes share similarities except green threads end up violating way more expectations and the code author may not have any indication or explicit mechanism to address this, like using AsyncLocal.

Also one change to look for is "Runtime Handled Tasks" project in .NET that will replace Roslyn-generated state machine code with runtime-provided suspension mechanism which will only ever suspend at true suspension points where task's execution actually yields asynchronously. So far numbers show at least 5x decrease in overhead, which is massive and will bring performance of computation heavy async paths in line with sync ones:

https://github.com/dotnet/runtimelab/blob/feature/async2-exp...

Note that you were trivially able to have millions of scheduled tasks even before that as they are very lightweight.

[0]: e.g. sending requests in parallel is just this

    using var http = new HttpClient() {
        BaseAddress = new("https://news.ycombinator.com/news")
    };

    var requests = Enumerable
        .Range(1, 4)
        .Select(n => $"?p={n}")
        .Select(http.GetStringAsync);

    var pages = await Task.WhenAll(requests);