Are you sure about that? First, many higher-order constructs boil down to simple first-order control flow after partial evaluation (see e.g. AnyDSL https://anydsl.github.io/#publications). Inferring stack size bounds in the presence of higher-order programming features is also possible, and was implemented (as the "static region optimization") in MLkit.

But the main point is that code in a high-level programming language looks very different from C or even Rust code. Sparks in Haskell, or processes in Erlang, or even individual goroutines in Go, are typically executing comparatively tiny programs. If the call graph of the program in question is acyclic, then it should be easy to get a bound on the maximum stack size.

To be clear, I agree with you that a 1:1 threading model is the better design for Rust, simply because it's the only design where you can guarantee zero overhead and don't need a complicated runtime. What I don't agree with is that the M:N threading model is inherently inferior. Especially for a high-level programming language, I would assume that you can reduce the overhead significantly through static analysis and a good implementation.