Unique keys don’t help much. It only takes one person to write a script and put on github so that it can dynamically find the key and unencrypted stored password.
Again it's a grad level thing, but many smart grads can work out why encrypting isn't better. At least of the many I've interviewed, even ones I didn't hire could figure this much out.
That said, the much greater problem is the idea of using a hard-coded key, instead of generating a unique key for each device/installation.