Regarding linking: you seem to be conflating concerns with libc's portability with the linking of libc. Libc is a portability concern not because of linking but

Regarding linking: you seem to be conflating concerns with libc's portability with the linking of libc. Libc is a portability concern not because of linking but because it is a worse-is-better compatibility layer. There isn't just one example of it, and it straddles the boundaries of the language ecosystem and the operating environment. If I write C targeting WASM and try to call fopen(), the build system either has to say "no" somewhere along the way, or bamboozle me with a very specific interpretation of what I mean by that, effectively turning it into an unspecified interface. When a language builds on that foundation it gains temporary convenience but misses out on being more encompassing in its approach to compatibility. Your statement only makes sense within a "libc is just the standard" worldview, which I believe contributes to the fragility problem by offloading compatibility into a series of "good-enough" measures instead of documentable specifications.