I guess the no_std/alloc/std split is sort of like what you're talking about? It's not an exact match though; I think that split is more borne out of the lack of built-in support some targets have for particular features rather than trying to cordon off subsets of the language to try to prevent users from burning themselves.

On that note, I guess one could hypothetically limit certain effects to certain Rust subsets (for example, an "allocates" effect may require alloc, a "filesystem" effect may require std, etc.), but I'd imagine the general mechanism would need to be usable everywhere considering how foundational some effects can be.

> Or are such language features beneficial for all applications?

To (ab)use a Pixar quote, I suppose one can think of it as "not all applications may need these features, but these features should be usable anywhere".