[tptacek]

Easy answer: the majority of exploitable memory corruption vulnerabilities in 2017 aren't simple buffer size calculation mistakes.

Pointer auth and control flow integrity techniques cover most (all?) memory corruption flaws, including memory lifecycle errors (which are probably the most common modern source of vulnerabilities). Built-in buffer bounds checks do not.

[hexadecimated]

One exception may be if you could steal an authenticated pointer to a buffer that's about to have some generated machine code written to it (e.g. for JIT execution), and use that to write your own arbitrary code instead.