Is css a bad design in terms of creating gui? [closed]

When creating gui, we handle two main issue: style and layout.

But css seems seperate the whole style and partial layout functionality out of html.

That means when handling with layout, we need consider html and css at the same time.

In iOS and android, we usually use something may called viewModifier or viewAdapter or uicollectionview etc... to control the layout, which enables nearly unlimited ability to determine the layout because we have a full access to the layout mechanism.

Meanwhile, creating renderTree by DOM and CSSOM is so slow and have many meaningless performance loss.

Why browser choose css for it's styling and layout? Is that because of the historical burden?

Why iOS and android abandon the way like css did?

What's the pros and cons of css comparing with other layout/style mechanism?

What's the future of GUI development?

Will css be the last straw to kill html and web?