Why do some of my posts get deleted? (iPhone)

It just says low- effort post, I comment on my own posts because it tells me to do so when I read the message. For example, I posted a post where I explained a trailer for Ninjago Dragons Rising season 3. I explained the context of a screenshot I took. I don't consider that low effort, I usually plan my posts for hours or at least one. Dozens of people ask simple questions in the Ninjago subreddit, and they never get deleted. Why is this?