for me it really starts with the home screens and most of the apps are arranged: the lower third of the mobile screen is underused while the top third is full of interesting things that I can hardly reach.

But you're right, of course. There are more and more action menues in the bottom right. But take a typical Apple app like Mail.app. In the bottom right there is only one action: write a new mail. The next step, after clicking it, is entering some information that in many cases will involve clicking something in the header field in the top third of the screen. Even send is at the very top right corner. Oh, the thumb movements...