Well, Selenium is browser automation tool and Appium is mobile automation tool. As far as they are created by humans, even you can create one yourself. But the question will be why do you need to create new framework. As it takes lot of time in creating framework and fixing bug. Also, Selenium and Appium have huge community to fix bugs. If you develop framework on your own to do the same stuff, it will take lots of money. If you want to create something open source, you will have to bring new ideas to the table which existing frameworks do not have implemented.
Selenium and Appium are very much stable and does most of your work. Also, they are open source and free. So, to develop something new to do the same thing will not help and does not make any sense as well.
There are certain frameworks and tools like Serenity BDD, Selenide, Selenium grid extras which are developed on top of selenium. That does the stuff what selenium does not. But they can not avoid using selenium.
Hope that helps!