The growth curve is different for different pages on Instagram (or across social media for that matter). If you have great content + active posting schedule, there is no reason people would not want to follow you. But are you able to reach them? Is your content appearing in the feed of people who might want to follow you? I am guessing, no.
So, here is what you can do:
1. Engage with people. Ask for feedback. Be open to suggestions and ideas.
2. Do you use hashtags? If not, start using relevant hashtags. Optimize hashtags to gain maximum exposure. Use different sets in different posts and see which posts do better.
3. Get influencers on board. And I don’t mean sponsoring. Just connect with the influencers. Comment on their posts. Share your work. Ask questions, etc.
4. Keep an eye on your analytics. After every couple of posts, stop and evaluate.
5. Run a couple of paid campaigns if you need a head start. But I think Instagram has a lot of organic potential if done right.