>Linux could be as great as macOS, but it's the fragmentation that kills it.
No, Linux is as valid technologically as the other offerings, fragmented or not. It's just that it doesn't have a mega-corp behind it to push, to make deals with businesses, schools, governments. As soon as Google stepped in with Android and ChromeOS, suddenly it was everywhere.
Android and ChromeOS just reinforce my point though. There is one Android™ and there is one ChromeOS™. I don't have to support Android with this package manager and another with that display server. I don't have to wonder what DE the Chromebook user has running, or whether they have a certain package installed that conflicts with mine. If those were concerns that had to be considered, would Android and ChromeOS have gotten as popular as they are? Food for thought.
I think what you describe is a necessary part of what I'm trying to get at, but not sufficient enough for it. So, yes, successful products tend to converge, because support and maintenance makes more sense that way. But products are not successful because of this convergence. If there was only one Linux, it would be about as popular as the myriad of them are right now. What it needs to be more popular is to be a product that a giant corporation pushes with all its might. Only that the standard PC market is pretty saturated - which is why a machine like the Valve Deck might be successful for Linux (or already is, if we consider some millions of sold units a success).
No, Linux is as valid technologically as the other offerings, fragmented or not. It's just that it doesn't have a mega-corp behind it to push, to make deals with businesses, schools, governments. As soon as Google stepped in with Android and ChromeOS, suddenly it was everywhere.