Why would it be safe for them to use an older recommendation system? It doesn't solve the problem, if their older system recommends a terrorism video, even if it only did so because that video came up chronologically, they're still liable.
I would think they would need to just stop allowing the general public to upload videos anymore and only permit trusted media companies and influencers (ones known to not create controversial content) to do so. Probably after being approved through a vetting process where their lawyers can look through at least some of the content first.