Comment by AuthAuth

Right off the bat:

1. Those loading spinners being bumpy pulled my eyes around the screen wildly to the point that they were experiencing pain. They need to be removed.

2. There is a status bar along the top, and an application launcher docked at the bottom. That's way too much vertical space being used, especially on laptops (which I'd wager is going to be the most used viewing modality for this OS). It should be merged into a single bar along one side of the screen.

3. The dropdown at the top left of each window seems to be taking up a lot of space. Especially when you're trying to fit four tabs on the screen. Get rid of it so the tabs can actually be read.

4. At 27 seconds in, there are two close icons in the focused window. That being bad could be a presentation all in itself.

5. Random padding in the status bar.

Unironically: win 10, or kde plasma - breeze dark.

I'm not a visual designer but heres what I think is making it look so bad. The task bar is way to thick. The flat design of the icons needs some shadows or something to make them pop a bit. The rounding on the corners is way to much and needes to be dialed back significantly. There is both a top bar and a bottom bar, pick one ffs dont waste screenspace with both. Also top bar is transparent while bottom is fat and grey. I'd keep the top bar and scrap the bottom.

As far as OS's that look good, #1 KDE Plasma with breeze, MacOS snow leopard, Windows xp and vista.

MacOS up until Catalina

Windows 7 with the Shine 2.0 theme

Gnome Adwaita

QNX Photon 6

BeOS R5

I'm sure there's more good examples. People here will say Windows 2000, but I don't think it has any grace.

Mac OS X Snow Leopard, GOAT

For desktop use? Windows XP. It's got the right balance of aesthetics and practicality. Windows ME also works, but is more utilitarian. Anything after 7 is just absolute garbage.