I have to wonder if job satisfaction at Facebook has a very binomial distribution. This is pretty much true at any large corp, where there can be a ton of variation between teams, but from the outside looking in it seems that Facebook basically has a dichotomy:

On one hand you have teams working on interesting and industry-leading tech, like React, GraphQL, Oculus, etc. But on the other you have legions of people working to make the money machine printing, and I've got to think most of that work sucks: the nitty-gritty of keeping the site up, content moderation teams, all the ad plumbing. A lot of that stuff would be good for a new grad to learn how stuff works at such large scale, but that's the cohort who I think would be most turned off by Facebook's social/brand problems.