It's hard to get data around churn rates as it depends on the company industry, pricing structure, audience engagement, etc. You will see anything from 2%churn for high engagement audiences to 6% for medium engagement, and up to 11% churn is something that is still common.
The highest percentage of people churning will happen in the first month. For some industries, the average LTV is indeed just three months, which can be discouraging. So getting people to sign up for an annual plan instead of the monthly is a great way to get higher ROI on a single client on average, even if you give a steep discount.
To help reduce your churn rates:
Do regular content updates. It will help your users want to stay to have access to all content.
Run promotional offers regularly (offering coupons can help with this).
Actively asking for feedback from your audience on what they like/dislike or want more of. You could create a survey for users that you send via email.
Check out your Analytics tab to see what your audience is watching the most. Consider adding more content similar to their interests or that builds up from that content they enjoy.
Review churn reasons provided with the canceling quiz, then act to improve from that feedback.