No matter which sort you use (except for new), content is recommended to you by activity. Depending on the sort (active, hot, top) it uses a slightly different mixture of votes/comments/time since post to determine the order.
The only exception is scaled, which boosts a little bit midsized communities, but still doesn’t manage to improve visibility of niche ones.
If lemmy is to truly start having active hobbyist communities instead of being 95% lefty US politics, Shitposts, and some tech stuff, it needs a sort that takes into account the user’s engagement.
For example, if I upvote / comment often in a community, there should be an option to have posts from the community be boosted in my feed, even if it’s a tiny community.
Let’s say I’m subscribed to !world@lemmy.world and !news@lemmy.world because I want to occasionally see news. However, I’m also subscribed to a couple hundred other communities, some of them who don’t manage to get more than a couple upvotes on their biggest posts. And whenever I see them I’m replying/upvoting because I’m passionate about that topic.
My feed shouldn’t be 95% c/news and c/world because those are the most upvoted and commented. I shouldn’t have to scroll down hundreds of posts to find “big” posts in small communities I interact with at any opportunity I get.
That’s why I think it would be beneficial to lemmy if the sort/algorithm took into account your engagement in a way.
It doesn’t have to be complicated, you can have a single number “engagement score” for every community calculated with a basic formula, and that number is used as a boost to the community.
I’m aware that there are some examples of successful niche communities on lemmy. But that’s mainly because either a significant chunk of the lemmy userbase is into that niche (let’s face it the lemmy community is not a representative sample of the world population, we tend to be very similar people), or because the posts on it are simplified image/video type posts which appeal to people who don’t know much about the subject.
This sounds like the sort of thing that's best solved with a 'favourite' option that pushes posts from favourited communities to the top of the feed. No need to get in there and over-complicate it with bespoke weightings or anything.
You are overcomplicating the issue by suggesting a "favorite" option when there is already a "subscribe" option. At the very least, consider proposing something distinct that helps users discover more of the small communities they are subscribed to, rather than suggesting something that has already been implemented.