SwiftUI’s strengths are layout composition, ease of animating, efficient dataflow, value-semantics, ease of changing things up, swapping in and out alternatives while prototyping, interactive hot-reload previews, making custom controls and layouts, and again, the ability to mix and interact with the classic frameworks wherever and whenever needed.

It can be improved in a bunch of ways, but once you’ve bridged the “missing parts” and embraced using it to layout and style and control classic frameworks while handling dataflow, it is just perfect. It is also as efficient as possible or can be made so.