I’m subscribed to quite a few communities now but my subscribed feed is still pretty barren. Whether I sort by hot or active I’m seeing the same few posts a lot of the time, often with very few upvotes or comments. I also see months old posts popping up again and again. There is a post on one community with -39 score from 8 months ago that I see every time I open the app. And one from 3 years ago with one comment from months ago.
All feed isn’t much better for me either.
Wait for your instance to upgrade to 18.3