give it time, people will come to their favorite instances with time. The best thing you can do is make your own posts to your favorite subs and cross post posts you see to other subs they fit into as well.
When I first arrived in Lemmy the top posts were about 100 likes and 5 comments. It has grown so much since then that I was already super happy but then this week they launch Boost for lemmy (I was a boost user on the before times) and now my life is finally complete again. Have faith guys, things will get better!