Look, if you nerds really want Linux Desktop to be a winner then it needs consistency and apps. There is no Linux Desktop that is consistent and 'just works', Linux Desktop a hodge-podge of crap.
There is no "Linux Desktop" -- not in the sense you mean. Various Linux distributions have created desktops with various styles and features. And they are more consistent than you think. Many apps have installation packages that allow them to be installed and work fine in multiple desktops. No doubt you have adjusted to differences in various Windows or MacOS updates. Adjusting to different desktops in Linux distributions is not onerous.
There needs to be native consumer apps like Outlook that don't need a special container or special interpreter to run, no skills required just run a native app, and yes there might be a cost for decent apps and they might be closed source too.
There are many such apps. See here for Outlook replacements. Most of them are free; some offer premium versions for a fee.
Until Linux Desktop is consistent, easy, and has native apps it will never really go anywhere. Keep hoping nerds, the proof is in the pudding.
I would argue many Linux distributions fulfill all three of your requirements. And Linux definitely has gone somewhere over the decades, despite naysayers like you. It runs on more hardware architectures than you know, small to large. You're probably using it right now (via servers on the internet) without even being aware of it.