I get the feeling we are now talking about two different things. If by “cracked” you mean that someone can rip and redistribute the content once they get access to it, sure, it’s very hard to protect against that.

What I mean is: it’s possible to restrict access to the service so that you cannot watch a video unless you’ve played the ad first or you are a paying customer. As an example: Netflix or any of the movie streaming platforms. There’s no add-on or special browser that allows you to use Netflix without being a paying customer, and if YouTube implements their plan, they can make it so you won’t be able to circumvent it just by using Firefox, like you claimed.