You are completely exaggerating the situation. I am using WhatsApp all day long and it's not that much of an issue. Sometimes messages don't appear instantly, so I have to press the back button and tap the message again. But that's it... Have you tried to reinstall your WhatsApp?
That's nice that your Whatsapp is working just fine. I will give you a run down of the problems i've had.
1, I won't get a notification for a message. I open Whatsapp and the message was sent sometimes over 30 minutes ago, ill get the notification hours later.
2, Messages auto deleting once they reach the top of the screen.
3, Only getting one tick on messages, but my friend gets the message anyway. Could take hours to get a double tick which confused me at first.
4, Not able to Email chat history to myself. When i try, the box doesn't even come up to let me select email.
5, Multiple lock ups and long loading times.
6, All messages sent from another person has "seconds ago" written under the message, even if it was sent hours ago.
Those are just a few and i've tried everything. Removing the app sorts some of the problems out, but after a while they creep back in. I find if i switch my phone off and on most the problems appear from that. Your app might be fine, but you can't say people are exaggerating the problems. I know people that the app wont even load. Just go have a look at the review section on the app and see how many people are having problems with it.