Such is the beauty of the fediverse, block/mute/filter freely and openly. I'd block and filter more if I weren't an admin. Curating your content is the purpose of the fediverse, you make the algorithm.
Sadly a lot of the good content will be lost, regardless of migration or encouraging users to take it off the site. Eventually someone in Reddit Inc. will have the "bright" idea to wipe everything out, to reduce spendings on data storage.
In the short term it goes as you say, they're selling API access to the LLM bubble. (And they're likely selling your data too, against your consent.)
However in the long term the LLM bubble will explode, and users will disengage with the site, causing a downwards spiral. At some point of that spiral they'll delete the data, after it's unprofitable. I think.
Reddit hosts hardly any content. It's a link aggregator.
All the text content, all votes, posts, comments, etc. probably only fill a few TB. The video and image hosting part is a bit later, but arguably not huge either. Given the salaries in the valley, just having a meeting with 10 people about deletion is probably more expensive than storage for the next 5 years.
I think quality hobby communities like the ones that used to exist on Reddit require both smart people and a larger population to create a sense of social investment. This kind of information used to be distributed across forums with fewer than 1k people each, which isn't so bad, but does prevent it from propagating easily.
I think social media is inherently incapable of fostering good content. By nature it is social as in interpersonal drama slanted. That's not considering shareholder factor yet. Early years reddit was an oddity at the unique intersection between message boards and the social media era. In the beginning they were in the money burning phase. Not concerned with making profit. So maximizing engagement at the cost of content quality wasn't on the table yet.
Quite frankly old reddits reputation became something larger than life sized. The expertise on reddit was never really that great. There was a lot of bad info but try telling a big headed neckbeard that.
Better content is to be found on the internet outside of social media. Find that person who hosts a site to share their content from a technical basis. The people who will not suffer fools. They want to talk about inner working of their widgets. They don't care about likes and subscriptions. They don't have shareholders to answer to.
Lemmy seems to be taking the route in attempt to rapid expansion by stuffing it with low content memes. A flaw is in trying to mimic social media when most people want message boards of yesteryear.