Is YC fun? Not the dinners. The work you're there to do.

It seems like doing a successful startup is closer to this than to fun: https://news.ycombinator.com/item?id=7222850

Maybe in the wake of a failed startup I deluded myself into thinking great teams are predicated on great friendships, a truism that no longer holds absolute truth.

Perhaps there's a misunderstanding of what a friendship is in a business context. The cofounders have to have been friends for quite awhile, otherwise the stress will tear them apart. But they probably don't have to be dear friends, or the kind of friend you hug. It's just business.

to those like me who held the institution on a pedestal

This seems the central issue. YC is ultimately about business. It's awesome, it's changed the world and my life, but having expectations that it's going to be fun and that you're there with dear friends seems off the mark. But I've never done YC, so this is just speculation on my part.