As can be seen in your screenshot I'm the second user with most reviews completed and will tell, from my perspective, you what the problem is:
Y U FLAGGING CRAPPY QUESTIONS AS DUPLICATED!?!?!?
Reviewing duplicates use a massive amount of time. The good reviewer have to read two questions, and answers to verify that both questions are actual duplicates. This would work fine if there wasn't for the 80% of reviews, that the reviewers have to see, don't even reach the category of "question".
How is a 1 line long "i haz a problemz, fix pls", without the proper information to know what is wrong in first place, a duplicated of anything but another unclear, vague question? You should have closed as "Unclear what you are asking" and ask for the missing information.
Since duplicated implies that the reviewer have to read two questions, please, think about the poor good soul that have to figure out what OP is asking first and then decide if the duplicated is actually what it's asking for. Remember, duplicated is the last close reason you should use, and only if the other reasons doesn't apply.
Y U USING DUMPING GROUNDS!?!?!?
I've seen people closing random "my wireless doesn't work, I don't know why!", that SHOULD be closed as "Unclear what you are asking", being closed as duplicated of My wireless/WiFi connection does not work. What information is needed to diagnose the issue?.
If you believe that the question need the information as explained in other answer, the Right Thing To Do™ is to leave a polite comment reading:
We need more information to know exactly what's wrong, please read this answer and provide the information required.
and flag it as "Unclear what you are asking". That way OP have a clear message of what they need to do, provide it, and possibly get their answers in a timely manner. At least, that is what I think it will happen... and in case of OP bailing out, the question is deleted and nobody (10kers) have to come along and delete it. Is a win-win situation.
Y U NO READING THE QUESTION!?!?!
And, sadly I'm still lashing out to duplicates, and this time not only affect reviews but also the users themself.
In the review queue, I find users flagging as duplicated questions where OP said, clearly, that they have read the questions, they even provide the link, and it didn't help them or have problems following the instructions, and instead of an answer, users just trow them in a loop, flagging them as duplicated of the very same questions they linked already:
And the sad part, is that reviewers just rubber-stamp this behavior. Those were examples that I got wind of because I was behind the reviewer, obviously not looking over their shoulders, but I'm sure there are many more cases.
If you don't feel confident of understanding a question/topic, investigate, ask around, but unless you are entirely sure, skip.
But I want to know how I encourage reviewers, how this help?
This is asking you to use more wisely the duplicated close reason. It's by far the most (mis)used close reason with pending votes in the review queue, and, as I've repeating in my post, is the most time consuming close reason.