First, this is a fairly non-productive place to ask this question: privileges are handled network-wide, so Meta Stack Exchange is the better place to ask it. There doesn’t appear to be any previous discussions of an idea like this, but you should probably do a more thorough search than the quick look-see I did if you want to raise it there. (Then again, worst that happens if you start it and it already exists is that it gets closed as a duplicate.)
Second, for the most part, privileges are not a reward. They aren’t given to you because you’ve worked so hard on things or contributed so much to the site that you’ve earned them or something. For the most part, the point of reputation thresholds on privileges is to ensure you understand the site well enough by the time you get them that you’ll use them properly. Having 3,000 implies you are probably pretty familiar with how the site works. That means you probably have a pretty good sense of how to use your privileges—including when you should not do so, because a particular case is outside your expertise.
Third, there is no privilege that allows you to break the site. There is nothing you can do that cannot be undone. And the particular privilege you’ve just received—close and reopen votes—requires four other people to agree with you before they actually do anything. Things you have a gold badge you can close or reopen unilaterally, but you have a gold badge in those subjects, you almost-certainly have a pretty good idea what is or isn’t a workable question in those subjects. Gold badges are not easy to get. And asking good, thought-provoking questions—the kinds that get a lot of upvotes—indicates that you do, in fact, know those subjects pretty well. And again, if you are wrong, it’s not the end of the world—you can undo it yourself, or five other people (or one other person with a gold or diamond badge) can overrule you and fix it. The amount of harm you could possibly do with this privilege is, in fact, so low as to be almost negligible.
Finally, the fact that you were concerned about whether or not your own behavior here has merited these privileges suggests that you are a conscientious, considerate user, which means it’s probably a safe bet that you’ll only cast votes to close questions when you’re pretty sure you know what you’re doing. For example, you may not know whether something in a system you don’t know is sufficiently narrow to be reasonably answered, but you’ll be able to tell when something is lacking a system tag entirely and therefore needs closing as unclear. It seems pretty likely that you’ll recognize the first situation and not cast a vote, and recognize the second situation and cast your vote—both of which are exactly what you should do.
The site isn’t asking you to magically know what to do with every question on it. It’s only asking for you input in the situations where you feel you do know what to do with one.
