Have you ever done native Android, including using the NDK?
It is full of arcane knowledge, scattered about commit comments, medium, G+ and Twitter posts from Android team instead of being on developer.android.com, APIs introduced in one IO are deprecated/replaced by the next IO, OEMs (cough Samsung) that change AOSP behaviours,...
So should we now measure who wins in arcane knowledge counts?
The Web lacks even the most primitive of UI primitives that desktop and mobile UI kits have had for decades. Virtual lists is the prime example.
You can't even reliably animate an element independently of other elements without breaking your entire page.
You can't pick an arbitrary group of components and place them in a different location of the page without them breaking in subtle and not-so-subtle ways unless you are extremely careful with your flat global namespace that is CSS. WebComponents solve some of that, extremely poorly.
And the list of things that are taken for granted in the desktop/mobile world is near-infinite. All of them have to be re-created from scratch, poorly, on the web.
Ah, like breaking Android UIs when dealing with fragment management or misplaced constraints on ConstraintLayout, usually only solvable after one finds the golden post on medium?
Furthermore, ConstraintLayout is a brand-new layout manager. Totally agree that there's bugs in it but nothing that could be called arcane knowledge. Do you have any examples for the actually arcane layout managers? Relative, Layout, etc?
Yeah, sure. Try animating an element without breaking layout. Trying animating an element that gets destroyed (oh, it's impossible, there are no events for when element gets removed). Try smooth animation while changing layout. And so on and so on.
Yeah, sure. If you constrain your entire animation to just the one box of a single SVG/Canvas/WebGL, then you can pretend that everything is fine. In reality when you try to animate anything, you're really constrained to animations that don't force re-flow. So, about 3 of them. And you have to be really careful (transposing an element's position will leave gaps).
Meanwhile both desktop and mobile have hundreds of animations big and small that are either impossible or extremely hard to do in a consistent manner on the web.