On Instagram, there are less people than Facebook. If you are not following enough people, your timeline might hardly have new posts. As you check Instagram over and over and find the same pictures, you might get bored. See why Instagram is so popular.
Even if you have followed some people on Instagram, you might still find it boring if you didn't follow the people who are interesting to you. See why Instagram is so addictive.
One of the things that makes social media rewarding is the notifications that people get. If you do not post often, you are less likely to get notifications, and so you won't find something interesting to do on Instagram.
According to a research by SimilarWeb, the time people spend on major social networks such as Instagram, Facebook and Snapchat has dropped between the last quarter of 2015 and the first quarter of 2016. This could mean that people are getting bored of social networks.
Instagram is all about pictures. If you are not photogenic, you might not be motivated to post pictures often, and so you might find Instagram boring. See why do I look bad in photos.
One of the posts considered boring by many users is the posts of food. People who don't like such posts can easily get bored if they have friends who post them often.
The more followers a person has, the more interesting Instagram will be for them since they will always find a motivation to post. When a person has few followers, they might not get many interactions.
Many people make posts that are not that relevant to their followers such as quotes, pictures of food and selfies. According to psychologists, irrelevant posts are considered very annoying. See why Instagram is fake.
Unlike Facebook where it's easy to add the people you know, on Instagram it's harder to get followers. The word follower creates some kind of a psychological barrier that makes it harder to gain followers.
On Instagram, people might feel disconnected when they see others having fun, or at least pretending to be, while they are in a totally different place and unable to join.
Attention seekers might find Instagram much more interesting than people who don't really care much about getting attention. See also why celebrities like Twitter.
Narcissists can find social networks very alluring, as they allow them to get the attention and praise they are always looking for.