People who are malicious or see an opportunity for gain will always abuse a system. Just because the DNS system has had to be patched to handle the abuse doesn't mean its badly designed. If it were as badly designed as your comment seems to imply it wouldn't be able to operate even half as well as it does.

The combustion engine's fundamental design is pretty damn good and that it had to be updated to handle unleaded gasoline isn't a knock (pun... intended?) against that design.