What would happen if someone hated a updated on a iPhone app?

What would happen If a person hated a update on a app?
I really want to know what should you do if a iPhone user hated a update on one of the apps. Like is there a way to get the old Version back. I just want to know. Like to say that someone updated their instragtem app and the user did not like the new disign what should that person do. Like is there a way to get the old version back. Or that person should just deal with it.

Unfortunately you can't change it back. Unless it was a minor change, you'll just have to get used to it. Otherwise, you should be able to give feedback and leave a message for them