You're signed in on lemmy.ca no? The stuff I see ain't so bad. A lot of the bad instances have been defederated. I also disabled NSFW content from appearing. And I block communities I don't want to see.
Press back while on the front page and you can pick the communities, you can choose All from there and then short by top 6 hours or something like that
Something to keep in mind is that just because a community hasn't been active recently doesn't mean it's completely dead. As long as it has subscribers, new posts will show up on their front pages and get votes and comments, even if it's been weeks since the last post.
The entire top/active threads are just the L4 bot (and 2 or 3 others) posting every article from a dozen online rags and the summary bot “participating.” Lemmy is still a desert of participation fluffed with 3 people who use it as their personal rss feed via bots.