The needs of desktop and mobile are different enough that it's extremely difficult to build a UI framework for both that doesn't seriously compromise one paradigm or the other.

I would argue it's one of the main reasons why frameworks like Flutter stuggle with widespread adoption on desktop — it was conceived primarily as mobile-oriented, and so on desktop you're stuck with half-baked third party components for essentials such as datagrids and tree views. WinUI with its mobile heritage in UWP suffers similar problems.

GTK + Adwaita tries to straddle the fence and produces a subpar experience on both sides. Desktop data density is terrible due to mobile-minded button sizes and margins (big touch targets, bloated whitespace to make inadvertant touch interactions less frequent) and desktop-oriented widgets like tree views feel out of place on mobile.

Web is fantastic.