Not to mention out-of-bounds access, uninitialized memory, invalid type casting, and a ton of insidious sources of undefined behavior

Use after free is generally VERY hard to exploit. Double free can corrupt data structures more with control. Use after free is basically at the mercy of the allocator and program state, where whatever gets written to the same memory address may or may not be relevant.

There is a reason why most vulnerabilities these days are either higher level logic bugs, or things that require code execution on the machine.