The desktop ship certainly has sailed - it's lost the home market as people use phones and tablets now.
> And on Android and ChromeOS, it isn't exposed to user space, so kind of irrelevant
Sure, and I can run Windows applications on Wine, so Windows is kind of irrelevant. Don't be silly.
> The only place where Linux really made it, was replacing expensive proprietary UNIX servers with free (gratis) clone.
Except you're forgetting that these expensive UNIX servers were supposed to be replaced by Windows NT (later Windows Server) machines. So you'd have Windows at every level and could hire a point-and-grunt "sysadmin" to run it all at a much lower TCO. That's the grand vision that we've been spared.
And you forgot about the embedded market. Hell, my TV runs Linux and I didn't even know (my wife chose it) until I was poking about in the menus and found a copy of the GPL. And you also omitted Cloud Servers, where Linux is hugely dominant. Oh, and Supercomputing where 499 of the Top500 Supercomputer run Linux.
But yeah, apart from embedded, phones, tablets, laptops, servers, cloud servers and supercomputers...what has Linux ever done for us?