these are the main things I care about, until a reddit alternative can provide this I'm going to stay mostly or frequently on reddit.

-somewhat reliable news headline feed from relatively neutral, serious center-right to center-left sources with little to no bad reporting/framing.
-reliably hear about social trends, but with some distance to them
-news discussion with some degree of different perspectives, some expertise, so it's not just all left to the popularity of the headline.
-discussion of movies and tv that is neither too fanboyish/popular leaning nor too indie/arthouse exclusive.
-collections of helpful pro-consumer information and resources, up to date megaposts in hobby communities
-a search function that will often enough lead to some helpful comments for most topics, googling "reddit xyz" was my go to for many years
-feeds for some types of videos, like publicfreakout, livestream clips.
-some communities that are more personal to me, like from my country or a political meme community, for venting and in-group discourse.
-control over what i see in my feeds, most recommendation algorithms and trending tabs just don't work for me
-control over where I engage with content and in what form it's presented, often I take a break from scrolling social media except for seeing some top posts in my rss feed. at some point I just want AI to read out summaries of all that stuff to me and actually visit website interfaces way less often myself.