This is a very slipery slope (where gcc/clang[llvm] just run onto): adding tons of attributes/keywords/"syntax features" which gives the compiler some semantic hints in order to perform "better" optimizations. There is no end to it, this is a toxic spiral of infinite planned obsolescence (and now ISO is doing the same).
There is also this other thing: extreme generalization and code factorization, to a point, we would have no clue of what the code actually does without embracing the entirety of the code with its "model". It did reach a pathological level with c++.
And the last, but not the least: OS functions are being hardcoded in the syntax of the language.
If you push further all those points they kind of converge: compilers will have keywords specific for each performance critical syscall, significant library function, and significant data structure for abstraction (some abstraction can be too much very fast as I said before). There is a end game though: directly coding assembly.