And this still permits oodles of memory safety issues. You can have lifetime problems with stack-use-after-return. You can have bounds checking issues on stack

And this still permits oodles of memory safety issues. You can have lifetime problems with stack-use-after-return. You can have bounds checking issues on stack allocated arrays. You can have data leakage through use of uninitialized memory. And while there are some kinds of applications where never performing heap allocations is viable, this design is simply not an option for a huge number of applications.