Dumb question, but have you tried changing from "Active" sort type (the default) to "New"? I had the same problem till I found that with lemmy's size at present, "New" is better at bringing you actually new posts from the past few hours rather than staying the same for days. Though maybe that only works for me because of the number of communities I'm subscribed to. Which is another thing that might help; discovery is a little difficult right now so best to use an external site like https://lemmyverse.net/ to find communities that interest you.