I've been half joking lately that if I wrote an OS, I'd call it Nostalgia OS. I'd aim for a UI reminiscent of windows 98 / windows 2000 / snow leopard. With HID guidelines and a rich, clear, cohesive set of UI widgets to build applications with. I think that was the peak computing user interface - at least as I experienced it.

Of course, the kernel would be based on capabilities (probably SeL4). And applications would probably ship as WASM bundles. And I'd have a built in local first user database built around CRDTs and things instead of a file system, kinda like a modern Lotus Notes. But for the UI? That era was great.

To some extent (not capabilities), Haiku fits the bill here (https://en.wikipedia.org/wiki/Haiku_%28operating_system%29). Applications are bundles (but not WASM of course). The UI is very clean. The whole OS is also elegant and very fast on modern hardware.

This is sort of what SerenityOS was going for. Alas it has slowed down a bit since Andreas now handles the Ladybird browser.

To be fair Ladybird is probably needed more urgently now.

> windows 98 / windows 2000 / snow leopard

I don't know if I would group those together. Windows 98/2k were visually similar, but OSX by that point was looking quite refined.

It had toned down the blue, but still had some visual flare.

95/98/2k had a very utility appearance. Just compare the recycle bins between each to see how much more effort went into OSX look and feel.

Check out the Chicago95 theme for XFCE.