The Android flat design is so similar to Apple's, and that's precisely because Apple copied flat design from Google and Microsoft. Apple should set itself apart from the culture-less flat design and go back to the the beautiful skeuomorphic design of iOS 6.
If you are referring to Google Material Design / Microsoft Metro then you are barking up the wrong design analogy.
There was no copying really. All three are very different. If anything Google have copied iOS with their weird Squircle app icons which look 'orrible as a folder.
Animations / Parrallax / movement and flow are all completely different. I really like some of Microsofts stuff ( but windows 10 is a awful mishmash of Metro and classic ( read 30 year old windows NT ) - If they had the balls they'd completely bin the old stuff.
As for skumorphic. It has its place in some apps but not in general UI these days - look at the mess iOS 5 became. and I never did get the quirky idea of having a 1930s TV for the youTube icon!