What if Android was designed in a way that meant the device makers had to modify only the UI and not alter the functionality of the features. Wont this have sol

What if Android was designed in a way that meant the device makers had to modify only the UI and not alter the functionality of the features. Wont this have solved their problems? Im thinking this because many phone makers just apply their skin on top of stock android and nothing more! Things like settings UI can be fixed for all vendors so that we don't get confused everytime we get a different phone! I hope fushcia does it this way!