Alas, web development "decided" to completely reinvent the wheel for all this stuff, leading to a new generation of heading-to-native toolkits derived from browser-based technologies, such as Electron, React Native and Flutter.
Unless you believe there is any mechanism to force a single cross-platform GUI toolkit on all developers - a belief that would make you basically insane - the reality is there will always be N different options for cross-platform development, depending on (a) which platforms you intend to cover (b) your own development history (c) subjective preferences (d) specific functionality that may be limited to specific toolkits.
Does it matter if N is 10 instead of (say) 5 ? I don't know.
Does it matter if the N is segmented into "derived from 90s widget models" versus "derived from 2010's web models" ? I don't know.
Is there any chance of a single toolkit that covers native desktop environments (which continue to be important for creative apps, high performance apps, browsers etc.), native mobile and browser based apps? I don't know, but it seems ... unlikely.