The ship has sailed for anything other than Windows or Mac as a mainstream, popular desktop. And it's sailing away from Windows and Mac too, towards phones and tablets. Mobile devices are "computers" for a profitably large number of people, and I don't see that changing.
That said, for this (literally) graybeard old UNIX admin, OpenBSD makes a great desktop. I like that it feels very much like my old SunOS, Solaris, and historic Linux machines, and I like administering my systems by editing simple text files instead of dealing with systemd/dbus/etc.* That said, I do still have an iPhone, and use it for the things it's better at.
* systemd is fine, dbus is fine, they do what people want them to do. This isn't a rant about those things. I've learned to deal with them in my professional life. For my own stuff, though, I want something that I consider simpler and easier to understand. I do enough fighting systems at work; I don't need it at home, too.