While I agree with you for the most part, their responsibility should not be fact checking. That should be left to the individual.
"According to the poll, 79% of Republicans and 73% of Democrats said social media companies have a great deal or quite a bit of responsibility for misinformation."
(https://apnews.com/article/coronavirus-pandemic-technology-b...)
Talk about "fact checking" you just make a statement about what people think and provided no evidence to back it up. That's the main problem here. Also "old media"?
So in short Facebook is doing way too little and doing it wrong too. But it does seem like the cheapest option for them to keep the lawmakers at bay.