There's like 3 components involved in making setuid safe (the kernel, the dynamic loader, and your exec), and at least one of them wasn't doing its job correctly (the dynamic loader). IPC by definition involves a superset of these components.
There's no reason to think that if you can't make a simple setuid binary safe, you can make IPC safe. IPC is an order of magnitude more involved. Specially because in order to gain any effective security you need a 3 way IPC (1st level = the client, which is completely untrusted; 2nd level = the request parser, which is trusted but runs without elevated permissions; 3rd level = the actual elevator process, which must run with elevated permissions).