Okay I hope I don't write a wall of text here but I usually write more than I should so sorry if that happens.
First, thanks for the video, it was an enjoyable watch (as most of your videos) and as someone who cares about UI look and ergonomics I'm glad you helped visualize the issues in the current state of things.
A lot of good points have been made in this thread, I didn't expect so many Linux users here in this forum but I was greatly surprised, I even saw someone mention Haiku which I think has great UI (and not UI) ideas.
Thus I decided to make a different point to what I intended in the first place, this will be a rant more about choices rather than actual UI design.
First, to add some context, I'm a long time (10 years or so) Linux user, however, I'm by no mean a Linux zealot, I never stopped using Windows (mainly because gaming) but secondly because I actually enjoy the Windows UI, it works well and stays consistent, I always more or less know what's going to happen. Linux on the other hand (and when I say Linux I'm generalizing of course because it's a huge environment of UIs) is usually much more buggy and inconsistent all over the place (ever used KDE with GTK apps for example?), and things break much more often.
I should also clarify that I'm not a huge terminal fan, I do use it because I'm a developer and we have to run a lot of commands during the day of course, but I'd say that I use the mouse a lot more than the average Linux power-user, I do not use tiling wms such as i3 or awesome or terminal apps when I have a GUI counterpart.
Now, to the point, I believe you make a lot of good points in the video, and I do believe the "perfect" UI is going to come from the Linux desktop (there's no such thing as perfect, but you understand), however, for that, we need a lot more developers and users, so we get more accurate bug reports, QA, etc. right now most of the problems dealing with the Linux desktop come from these little annoyances that would not be there if we had more users to report them and more professional designers and testers in the development team; the problem is that this is not going to come until more people start to use Linux and help visualize these problems.
Therefore, I completely understand that you might not want to use Linux as your daily driver because you mostly deal with gaming and video editing, and that makes perfect sense, however you must understand that Microsoft does not care about what you or other power users think because put simply the percentage of people who are willing to make a 1h video about the topic and completely change the Windows shell is near 0; the percentage of Windows users who complain visibly about anything at all is bigger but still insignificant to Microsoft's business plan.
Even more, they will probably try and close up even more the Windows ecosystem by not allowing shell replacements or such, they do not want more complexity added to the codebase than what they already have, and they want to avoid potential security issues or minor annoyances that can occur from giving the user more control, because 98% of Windows users (made up percentage of course) don't care about customization or ergonomics, because they type at 20WPM anyways.
Linux is a completely different deal, when GNOME decided to move from GNOME2 to GNOME3, Mate was created so that users could stay with the same workflow, there are also KDE3 forks, XFCE is pretty much the same from 12 years ago, etc. Besides, whatever you want, you can customize, but you and the rest of the forum already know this so I won't keep trying to make a point here.
However what we really need are more users like you which have a critic eye to question what's wrong and provide alternatives, but which also have the popularity to change people's minds and show Windows users that Linux isn't so bad and they should try it out, if you really care about issues like this, you gain nothing by consuming Microsoft products and perpetuating their OS monopoly, the point for better UIs can be made, but in a platform where you really have choice and a voice to be heard.
More users on the Linux desktop would mean more money to polish things up, to hire driver developers, would mean more incentives for game and software companies to develop with Linux as a target, etc. As I said before, I'm a Windows user as well, I'm not some kind of Linux anarchist even if in the last paragraph I might've sounded like one, but I really wish I didn't have to use Windows.
Thanks for reading if anyone made it this far.