Yes, you're right if you take it that way. I didn't mean the internet is built exclusively with open source software, but the majority of developed applications contain at least a bit of open source software, like a library, curl, Apache, PHP etc. That's much closer to 100% I think. Something where you can say "we took something for free, we give something back". Not that that's required in any way.

There's some high profile exceptions like the infrastructure parts you mentioned, but noone expects you to open source your router and unix config, there's nothing worth contributing and collaborating on here.