For me, the content created by communities that is exclusively available on that site is really helpful to me. If possible I would definitely try and archive a few subreddits and write something to search and access it offline (sorta like https://en.wikipedia.org/wiki/Kiwix but for reddit).
Even if the Fediverse catches on and that Reddit goes down the way of Digg, Reddit will still remain a goldmine of information for years.
Pretty sure there is an option for people to delete their data when they delete their accounts though. I think a fair bit of info will be disappearing soon
Which is really sad when you think about it. It’s a blow to our collective knowledge.