There isn’t any app on windows or linux that can match what Preview does.

One thing you may not know about is you can map anything in the menu bar to a keyboard shortcut. The application doesn’t even know you did that. That’s an operating system feature that neither Windows nor Linux can implement reliably.

Accessibility is another one.

It’s like this all over the operating system. There’s a deep integration with the apps and the UI you wouldn’t notice unless you’re a power user.

What does Preview do that's hard to match?

Genuine question. I've been a Mac user for decades and on balance think it's quite good, but Preview is one of the most deeply frustrating, buggy, and unintuitive pieces of software on the system--it's at the top of the list of things that I wish I could swap out for something--anything, MS paint would be fine--else that was as deeply integrated in Finder/image/PDF interactions.