Following is not a “choice”, but an obligation.
Joseph, perhaps this is a semantics thing. We have bechira and can choose if we want to follow halacha or not. If we choose not to follow, we are going against halacha and there are consequences to that.
As for the rabbonim saying “maariv at 11 am” – the rabbonim have leeway in how they pasken, but if they try to change something to be against halacha, you arent supposed tofollow. I could be wrong about that, but thats what I was taught (and no, I am not specifically talking about maariv at 11).