OK...I wasn't reading all answers because lack of time and I've also promised that I won't post on GFY without good reason because of average IQ of people here ( i am starting to believe that stupidity is contagious), but this thread is actually useful.
To help people calm down, next is my opinion:
None of the tools we are using is 100% precise, not even close. Yoast is good but it is not a serious onsite SEO tool. It helps, a lot....at least until there is a good competition for a specific term. Readability feature can make panic but Yoast is missing some of the most crucial things for a proper analysis because there is simply no good engine behind it that will take onsite parameters into consideration. It is more like a grammar tool (readability section we are talking about here). Otherwise, everyone using Yoast and making it all green would be at the top of SERPS.
Maybe, at some point, grammar will be considered an extremely important thing like it recently happened with mobile site speed requirement but I personally don't believe because it would be too hard to achieve and there are hundreds of different languages in the world. Keep in mind that Yoast has to give some improvements to motivate people to buy their products.
The first thing I 've noticed at the beginning of the thread, while I was superficially reading what is going on, is that review requirement was 500 words. Even without doing a check I can tell that this is simply not enough for a good ranking considering the targeted subject (most important porn sites and their reviews).
But what I wanted to tell is next:
Below are print screens of two of my pages ranking #1 for some of my targeted keywords. These are serious articles, which means not a luck or something like that but the result of planning and analysis that resulted in good positions and sales.
#1 - ranked #1 in google.com and google mobile with a length of 2294 words
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#1 - ranked #1 in google.com and google mobile with a length of 1847 words
Additional info:
- both sample keywords are ranking top in Yahoo and Bing
- Yoast is giving info that it is not necessarily good, or at least, not useful. Take a look at their advice saying that the recommended minimum is 900 words (for a cornerstone article). There is no such thing. Every keyword requires analysis where you will sort top rated pages for some keyword and then count their length. This will give you info what is enough (at this moment) from Google's perspective to be ranked well. Sometimes you will see sites with only a few sentences and that (usually) means that competition is weak. But that's another story. Similar is with other things Yoast is often suggesting.
- you can have millions of words article but it will be useless without a proper domain authority (link profile) and without quality article really talking something useful about the subject (giving answers to questions, pointing to other resources, explaining things, etc).
- I am not selling you anything. Don't bother to order SEO services, I am buried in work. Need to say this because there are tons of retards lurking and stalking around GFY that will use every possible chance to say something malicious if they notice a useful post.
Hope I've helped to ease the tensions with precise samples above, there are other things to care about SEO, Yoast is at the bottom of the list.