Consistent look is nice, but when talking about "native" UI, I really care about reliability and seamlessness.

Custom UIs tend to be crufty; slow-ish, sluggish, they don't quite integrate with OS conventions (right-clicks, C&P, tab, overflow behaviour, scaling, rendering quality, window resizing behaviour and so on). If a custom UI is none of those things, and not really ugly, I don't think I mind. For example, I never played a computer game and thought, nice game but why are the buttons so custom?

I think the "native look" requirement got further diluted in the last decade with the rise of so many new platforms. A while back, it was mostly Windows; Linux was less popular, and frequently TUI anyway, Mac was perhaps more niche. Java GUIs were a thing and not very well-received. But then at least these "platforms" came on with different, high-quality, "custom" UIs: Android, iOS, Electron (it has its own custom feel to it), generally web apps, and so on.

So I'm desensitised to native "look", but not native "behaviour".