God of war 2 ran on 32MB of ram. There is enough ram in the devices for any reasonable workload. Just the developers on all levels of the stack weren't bothered to give rat's ass for optimization.

The current crunch and constrain in compute is great time to show once again some ingenuity. The lowest level of smartphones from couple of years ago have more computing power than XBOX 360. That should be enough to run Whatsapp smoothly.