If you subscribe to those subs then your home page will be just those subs. If I go to all I get memes and politics. But I have noticed posts in "groups" and think it's mostly bots on subs hitting specific target times for engagement.
Lemmy [All] shows whatever it considers the highest upvoted and trending no matter the community or instance, as long as yours is federated. Switch to Lemmy [subscriptions] or Lemmy [Subs] to see communities you are apart of.