This is a very serious and fundamental problem !!! 
on iOS phone after page switch (for instance on click “back” button and change page to main) there is 1-2s delay on which tapping or clicking is block.
Because this behaviour user have experience that app is broken because need to click twice on button to work.
I try to find some solution but only found this (change file app.module.ts):
IonicModule.forRoot(MyApp, {
pageTransition: 'md-transition'
}),
This solve delay problem but it is unsatisfable because app page switching not look like in native app (pages not switch from left-right but transparently appear/disapear in bottom direction). Any idea?
Here is similar question asked 5 months ago on stackoverflow: