What if Metro was done by anyone other than Microsoft?

What would you consider "done right"? The main problem with it was that they used it on a desktop computer operating system. I'm sure it was just fine on Windows Phone.
- Worse, they even forced it on Windows Server 2008 (and 2008R2). That interface had no business being on servers which many times only were only accessible by narrow higher latency remote links and many times without mice.
  
  It is argued by "some" that a GUI has no business being on a server.
  
  2012, 2012r2*
  2008 was "vista", r2 was 7.
  
  Why would you even consider using Windows without a mouse, though?

Wasn't that the UI overhaul that started with win8 and persists to a lesser degree to this day? It's impossible to make an UI that works efficiently for both desktop and tablet. They're two different platforms that are operated in different ways, and as such different UI designs are needed. Trying to unify them is like trying to invent a dashboard that works for both Volvo 940 and Airbus A380.
If so, I'd say it couldn't have been done "right" by anyone else either, as it seems that a core element of its design is to make information as vague and short as possible, while padding it with a lot of dead space. At a distance it looks neat, but up close it feels like you're expected to play guitar with mittens on. Its only reason for existing was that it was built on logic that was flawed to begin with.
And any implementation would've run into the same issue: You're removing flexibility for the sake of simplicity, something you cannot really do with a desktop OS. Microsoft never seemed to grasp this fact.
Example, if I want to change the thingamajig-ratio of the skoodleblurp, utilizing the brumblebork method:
Linux: skoodle -s thinga 50 (brumblebork is assumed by default unless something else is explicitly defined via --method=)
msdos 6.0: skoodleb /thing 50 /brumblebork
win 3.x and win95: can't do that natively, but the msdos method still works for some reason.
WinME: Nobody knows how it's done, or even if it's possible. Anyone who wants to adjust this is smart enough to avoid WinME
win2k: after right clicking my computer and selecting properties, it's a setting hidden somewhere in the hardware tab, provided you're running the latest SP.
win98: same as win2k, except a reboot is required afterwards
XP: same as win2k, except a defrag is required afterwards. Also, Teletubbies color schema.
win vista: back to rebooting. The change may not have been applied. It will not tell you either way.
win 7: finally they made it functional and easily accessible via the control panel
win 8: uh oh, the control panel of ye olden days is no more. We have a new thing going, so there are two way of doing it. The newer method isn't quite as flexible as the old control panel, though; you need to regedit for proper brumblebork.
win 8.1: They fixed the new panel, but you can't fit it on a single screen due to excessive dead space padding. And sometimes you get told to contact the sysadmin. For your computer. That you own.
Win 10: It fits on one screen now, you just have a million sub-menus to navigate through; control panel -> network -> advanced -> skoodleblurp -> advanced -> thingamajig -> advanced (yep, again) -> ratio slider -> apply -> OK -> submit -> execute -> "are you sure?" -> (three minutes of that spinning circle that replaced the hour glass) -> Fuck, you forgot to check the brumblebork box half an hour ago. At this point it's easier to get WSL up and running and then run skoodle -s thinga 50 --method=brumblebork (method not implied. WSL isn't that good)
Win 11: you have to log in to support.microsoft.com with your Microsoft account, using edge, and hope it has detected that you are running an OS that supports this. Then you can download a service patch that may or may not be relevant. Either way it changes your default search to Bing.
I think I got a bit carried away there... but my point still stands. It was an awful design choice, and the awfulness was part of its core functionality. It's gotten a little bit better since its initial release, but it still sucks.
- You missed
  winMe: you can't change the thing because the OS already crashed.
  
  Thanks for reminding me of that abomination. I edited in my own take on that inOperable System
- Hmm.. In my mostest most humblest of opinions, no, you didn't get carried away. You explained it in just the right amount. Maybe even stopped too soon, would have loved the version for Mac.
  
  I'm afraid I know fuck all about Mac except right clicking requiring a doctorate, and it having a pretty cool screen saver game in the early-mid 90's
- XP: same as win2k, except a defrag is required afterwards. Also, Teletubbies color schema.
  The Teletubbies color scheme was great, though!

Metro was great on Windows phone. I still miss Windows phone 7 & 8.

Then no one would have noticed and sysadmins everywhere wouldn't have their PTSD triggered by the words "charm bar".
Shit, now I need whiskey.
- For those of us not in the know (or who have suppressed it), wtf is a charm bar? All Google points to is 90% jewelry and 10% generic metro stuff.
  I didn't use Win 8 or 8.1 for long, though. And i've only used 10 and 11 via work, set up by a pretty reasonable admin.
  
  It was the auto-hiding replacement for the task bar. You opened it by moving the mouse pointer to the upper right or lower right corner. But unless you remembered where it was at, you'd get stuck asking, "where the fuck is the start menu". It especially sucked when you were a normal version of windows and RDP'd into a Sever 2008 box and couldn't use the Win key.
  
  It's this strange, strange in-game-style menu that pops up if you pull from the right(?) edge of the screen in Windows 8

Remind me what Metro was again?
- This design language

I'm using it as a skin on my Android device now. It's a great UI. But it was built for an unwanted platform.
- What r you using for the skin
  
  Square Home. I think I had to pay $3 for lifetime access to some features. It's worth it, IMO. Has widget support and a few other nice features.

Using a chain saw to hammer in nails is always going to be shit no matter who designed the chainsaw.
It's the wrong tool for the job on desktops.

Oh fuck, I forgot about how awful this was.

I'd say Metro was fine, but it was mainly made for Windows Phone and the Zune HD, and in my opinion, only works well on these two. When forcing it on other platforms where it doesn't feel natural, such as the Xbox 360 or the desktop versions of Windows 8 and 8.1, you get a pretty poor user experience due to the design language made primarily with touchscreens in mind. People got confused as to how to navigate their devices.
As for me, I quickly adjusted to Windows 8.1, so I didn't hate it that much.