Consistency is a large factor in any good design, UI design more so.
They have internal consistency. The iOS version looks like the macos version which looks like the web version, etc.
This upsets HN users but the rest of the world decided that apps looking like windows built ins doesn't matter.
OS-level consistency is also consistency. It depends what we value. A lot of apps’ design could’ve been basic, OS-like UI. Apps such as GymBook or WhatsApp are internally consistent while still adopting many elements from the system’s design, instead of reinventing the wheel.
Within OS consistency is much less of thing a thing than Web design conventions. Windows by itself has had several different UI frameworks over the years, so different "native" Windows programs can look completely different from each other.
There are two types of consistency in this context: consistency within an OS and consistency across them. I, too, prefer the first because I only really use one OS, but this preference varies. I don't think it's right to say that the first case = "ui toolkit", but the second case doesn't.
A foolish consistency with terribly designed shallow superficial desktop user interfaces dreamed up by overpaid cocaine addled corporate boutique brand designers with not only no experience but actual burning contempt for usability and human factors and accessability and affordances is the hobgoblin of little minds.
That’s why HN users constantly advocate for Vim, a program in which every single thing works completely differently from every other modern application.
Consistency is the reason why Electron is great. Consistency of the UI across operating systems.
Consistent like what? Like maybe a decade ago one could say that osx was consistent, but nowadays even SwiftUI and cocoa is visibly different, let alone every second app that uses electron. And people don't care.
Windows has like 4 frameworks available on a bare new, latest OS install, just go deep enough in the "settings" or whatever they call it, and you can reach down to winforms. And on top the start menu is a react element!
(And in Linux you have the gtk and the qt world, and everything else)