@Frode As noted in the rules, "Any post breaking these rules can be flagged." Off-topic posts would be breaking Rule #2. Feel free to flag in those instances and/or contact the moderators privately, as @Ramiro Espinoza noted.
It is unfortunate that we can't rename the Abuse flag to something more intuitive.
The changes are not about the meaning of the flags. The changes are about the limits of the forum software (and the complaints of our users). We can't put Off-Topic under Flag, for example. There's no Flag other than Abuse that will send a post to the moderation queue at this time.
As noted in Rule #4, people should flag responsibly.
If removing some of the flags means people will have to be more communicative, then, maybe it's time for that. Designers are communicators, after all.