For me, the biggest benefit of the university structure was 1) teaching me things I didn't even know existed and 2) teaching me things I didn't think we're important (but turned out to be).
(1) might be solvable with an online curriculum, but (2) requires an evaluation or end-game credential to force me to do it.
Other than that, as you mentioned an even bigger benefit was social, the shared experiences with others, and the cross pollination of ideas from these other people