The problem is that that does not release you from your contractual obligation to pay every month. The company is still free to (and often does) send you to collections.
You mean this case? Why should that get it dismissed?
This is about abusive (and unlawful) business practices, not a lack of knowledge on the consumer's end. If the customer had full knowledge of the terms before agreeing it would still be unlawful, the law generally doesn't care that the two parties consented to an abusive business relationship.
But ye it is not optimal. You'd probably want to have some record of trying to cancel.
It's slowly getting to the point where a low credit score will bar you from participating in major areas of the economy.
1: https://www.experian.com/blogs/ask-experian/what-is-credit-c...