Well you wouldn't be using it if it was sucky and useless. Just because it lacks an option you want it doesn't make the app unworthy.
You can always check your "Following" list and see who approved you. It shouldn't be difficult unless you mass Follow/Unfollow people all day. Alternatively you could use a third party app and track your account activity, ghost followers, unfollowers, new followers etc... there are too many apps that do just that. Instagram is not the kinda social networking platform where you have to follow thousands of profiles, a few are more than enough.