The interesting thing is that had OpenDoc took off, the Mac would’ve moved more toward the component-based ecosystem that you describe instead of an ecosystem of monolithic applications:
https://youtu.be/oFJdjk2rq4E
Alas, OpenDoc was a product of “interregnum” Apple, a font of innovation but had no singular vision (OpenDoc was one of many visions Apple promoted in the mid-1990s as the future of Mac development) and a track record of failed projects (Pink/Taligent then Copland). When Steve Jobs returned in 1997, he brought and enforced a singular vision for the Mac, one that revolved around NeXT technology. OpenDoc was killed under these circumstances:
https://youtu.be/oeqPrUmVz-o