[sansnomme]

To be fair, if you want it to be that pretty you will have to either reinvent two-thirds of a browser or half a game engine. There's a reason "rich UI"s are a pain to build compared to native GUIs (MSFT Xaml is more similar to a web browser than traditional winforms-style UI).

The best compromise right now is to aggressively build pretty, heavily themed prebaked designs. Think Material Design, Cupertino etc. so native UI is somewhat good looking too even though it may not be as "rich" as a React one with all the drag and drop animation and flashy trinkets. Feature wise of course there's only marginal improvement to old school Java Swing, but it's certainly easier on the eyes.

[comex]

Maybe on some platforms. I'm a Mac user, so speaking for that platform, AppKit has had built-in animation support for over a decade (and now with Catalyst you can also use UIKit if you want). Drag-and-drop in particular has animations out of the box when using certain built-in widgets – e.g. when you're dragging an item into an NSOutlineView, the existing item at the cursor will slide down to make room for it. (But what in Slack is even draggable? I can't seem to drag to rearrange channels, for instance.)

[sansnomme]

Exactly my point, OS X has tons of prebuilt designs with knobs for customization. But at the end of the day they can still be built rather quickly. Drag and drop the components in Xcode, tweak a few variables and animations here and there and you have a perfect looking app that is coherent and consistent with the rest of the system. On the other hand, a modern successful SaaS requires hundreds of man hours of work just on design and UI alone. For web, nobody wants consistency. People gets upset if every site looks exactly like bootstrap. Sites have to be styled, branded, made unique. Yet for traditional desktop i.e. not electron, the moment a cross platform native UI library look vaguely off, devs throw a fit. Think Gtk, Qt, Swing etc.