You've certainly gotten me thinking about this for a few hours now. I think both your arguments have holes:
a) Using stuff other people made doesn't require collaborating with them. Not even in the world we live in today, let alone the more idealized one where more becomes possible. I discovered
http://minimal.linux-bg.org a month ago and within 2 weeks had distilled what I needed from it to create bootable disk images of Mu.
b) There's no argument that collaboration is important to any creation. It's key to what I do. But is it
prime?
(Me, I think preserving a sense of motivation is prime. And expecting 'collaboration' can often be motivation-sapping:
https://www.teamten.com/lawrence/writings/plan05.html. I build to enable collaboration, but I treat collaboration as something you sow seeds for and wait a long time to see bear fruit. Collaboration shouldn't be on the critical path.
But that's just me, and this is just an example to show that there are other paths forking off where you think there's a straight road.)