I don't need it for Amazon Video? Are you sure? Then what am I paying for? I certainly don't intend to ever buy anything from Amazon, they just have a handful of really good shows.
Just a warning for what it’s worth: I have heard of some heinous dark patterns with cancelling Amazon Prime. (This thread is reminding me to do that myself.) I would be skeptical of any “Success!” messages until I’ve crossed several layers of “are you really super duper sure with a cherry on top?”-hell. And even then... probably wanna double-check.