It's because the historical perspective in this article is really lacking, despite that being the premise of the article.

Not only does the author seem to believe that C was the first popular high-level language, but the claim that hardware provided stack based CALL and RETURN instructions was not universally true. Many systems had no call/return stack, or supported only a single level of subroutine calls (essentially useless for a high level language but maybe useful for some hand written machine code).

FORTRAN compilers often worked by dedicating certain statically allocated RAM locations near a function's machine code for the arguments, return value, and return address for that function. So a function call involved writing to those locations and then performing a branch instruction (not a CALL). This worked absolutely fine if you didn't need recursion. The real benefit of a stack is to support recursion.

The prevailing opinion seems to have shifted towards using the frame pointer for its special purpose, in order to improve debuggability/exception handling?

But the article is really quite misinformed. As you say, many mainframe/mini, and some early microprocessor architectures don't have the concept of a stack pointer register at all, neither do "pure" RISCs.

I'd argue there is a real "C Stockholm Syndrome" though, particularly with the idea of needing to use a single "calling convention". x86 had - and still has - a return instruction that can also remove arguments from the stack. But C couldn't use it, because historically (before ANSI C), every single function could take a variable number of arguments, and even nowadays function prototypes are optional and come from header files that are simply textually #included into the code.

So every function call using this convention had to be followed by "add sp,n" to remove the pushed arguments, instead of performing the same operation as part of the return instruction itself. That's 3 extra bytes for every call that simply wouldn't have to be there if the CPU architecture's features were used properly.

And because operating system and critical libraries "must" be written in C, that's just a fundamental physical law or something you see, and we have to interface with them everywhere in our programs, and it's too complicated to keep track of which of the functions we have to call are using this brain-damaged convention, the entire (non-DOS/Windows) ecosystem decided to standardize on it!

Probably as a result, Intel and AMD even neglected optimizing this instruction. So now it's a legacy feature that you shouldn't use anymore if you want your code to run fast. Even though a normal RET isn't "RISC-like" either, and you can bet it's handled as efficiently as possible.

Obviously x86-64 has more registers now, so most of the time we can get away without pushing anything on the stack. This time it's actually Windows (and UEFI) which has the more braindead calling convention, with every function being required to reserve space on its stack for it's callee's to spill the arguments. Because they might be using varargs and need to access them in memory instead of registers.

And the stack pointer alignment nonsense, that is also there in the SysV ABI. See, C compilers like to emit hundreds of vector instructions instead of a single "rep movsb", since it's a bit faster. Because "everything" is written in C, this removed any incentive to improve this crusty legacy instruction, and even when it finally was improved, the vector instructions were still ahead by a few percent.

To use the fastest vector instructions, everything needs to be aligned to 16 bytes instead of 8. That can be done with a single "and rsp,-16" that you could place in the prologue of any function using these instructions. But because "everything" uses these instructions, why not make it a required part of the calling convention?

So now both SysV and Windows/UEFI mandate that before every call, the stack has to be aligned, so that the call instruction misaligns it, so that the function prologue knows that pushing an odd number of registers (like the frame pointer) will align it again. All to save that single "and rsp,-16" in certain cases.

This. They're shouting at the sky from whatever squirrels are running around their brains without understanding anything about real CPUs. It's somewhere between a shitpost and AI slop. They offered no better alternative except to bitch about how "imperfect" things are that work. I'd like to see their FOSHW RTL design, test bench, and formal verification for a green field multicore, pipelined, superscalar, SIMD RISC design competitive to RISC-V RV64GC or Arm 64.

XMOS still very much alive. But CSP comes with its own set of challenges which ironically have force one back to using shared memory.

It's too constrained to statically-analyze the whole program to determine required stack size. You can't have calls via function pointers (even virtual calls), can't call thirdparty code without sources available, can't call any code from a shared library (since analyzing it is impossible). This may work only in very constrained environments, like in embedded world.

Well, you can check out the iAPX432 to see an architecture with message passing hardware, and see how well it worked out in practice.