I can render Metal shaders trivially in SwiftUI. Rendering glows, and blurs, and animated effects is much easier in SwiftUI than in UIKit, just use `.blur(radius:)` or `.blendMode(...)`
I have used AppKit and then UIKit since its inception. Creating visual effects like layer masks that modulate the opacity of underlying views is trivially easy in SwiftUI — far easier than the boilerplate and constant bookkeeping that CALayer's mask requires.
So a lot of the advanced full-screen animations in some of my games and apps are SwiftUI, because they are performant, provide the cool effects and animations, and work great. A lot of the simple get-the-job-done views and tool palettes in my apps are also SwiftUI, again because they don't ask much and get the job done, and look great.
However, where SwiftUI falls down is exactly what was demoed in the video: large collections of thumbnails that fetch asynchronously? Use UIKit. Multi-thousands of items in large, complicated lists? You can try SwiftUI, but you'll need to learn how to optimize it.
Other things, not mentioned in the video, that are more annoying in SwiftUI: want to take control of a transition between views, end-to-end? Not really possible in SwiftUI. There are bugs with ZoomNavigationTransition that affect all of Apple's own apps, and you aren't gonna be able to fix them without switching to UIKit.