I don't care too much about the UI widget style as long as the implementation is good and responsive. I tend to use app in fullscreen (F11) with minimal chrome and to be honest I kind of like when each app has its own UI style, especially if it can be user-configured with themes.
Apple/macOS users tend to fall in the other category, following the Apple guidance, where all apps should look like they were made by the same company.
Mac users don't want all GUI apps to look alike; however, they should follow macOS UI/UX guidelines regarding copy/paste, drag and drop, keyboard conventions, etc. The whole point is to not have users having to relearn these basics for every new application.
Developers generally get these conventions "for free" by using the frameworks built-in to macOS. That doesn't prevent developers from creating custom, stylized interfaces if that's what's needed.
Even Apple's pro apps (Final Cut, Logic, etc.) look quite different from those that are bundled with macOS such as iMovie and Garageband.
No idea what a Windows app looks like, though, I recently fixed my grandfather's Windows 8 laptop and immediately gave up trying to understand how theming is meant to work.
I now focus on making my shell/terminal environment as good as possible and ignore GUI land whenever possible. Which today pretty much means 99% of the time I'm running a bunch of terminals and a couple web browsers.
But beyond that, it's a mirror of the graphical side. I mean, it's not like the GUI invented a lot of new widgets, either. There are still buttons and menus, it's just that they look and behave differently in each app. The same goes for the CLIs, where there's no rhyme or reason for all the long/short parameters, sub-commands etc.; To use the git metaphor, we're in a bathroom where all the porcelain is coming from different manufacturers and your got your brutalist toilet bowl next to your gold plated sink. And nobody knows what to do with the three shells.
libui seemed like it was going to be this, but it looks like there haven't been commits in almost 2 years :(
(I'm mostly replying to raise visibility on libui, maybe someone will discover it/help out a bit)
IE. IMO that ship has sailed and using lower level/cross platform graphics stacks make a lot more sense these days.
Native-ish interfaces are still pretty prevalent on mobile though.
Oh how they laughed when Sun tried this with Java some 25 years ago...