A phone could be a mediocre PC. In my opinion, it will not gain any significant market share competing against other PCs -- mediocre ones, good ones, great ones, and "insanely great" ones too.
I don't think we can fairly compare a phone pretending to be a desktop against other desktops.
It would be more fair to compare a phone that has desktop features, to a phone that doesn't have desktop features.
So let's compare the best Apple phone that refuses to have a dex like experience; to a Samsung that has had a dex experience for about 10 years, or to a Google phone that is now adopting desktop experiences.
If the future is anything like the past, in 5 to 10 years from now we'll see a desktop experience on iPhone and they're going to be snobby about it.