This answer is strongly in line with Nick Stauner’s and Laura’s, but I want to give the following argument that I believe to be straight to the point:
The main decision that reviewers in the low-quality queue have to make is not about quality, but on the correct placement of content. Therefore any naming of that button that somehow suggests something about the quality of posts is inherently flawed.
In some more detail:
Certainly, improving the quality of posts is one of the purposes of the low-quality queue. However, the first decision a reviewer must make is whether a post should stay at all, i.e., there is any point to improving it. After all, many posts in the low-quality queue are spam, closeworthy questions, not-an-answers, comments posted as answers, questions posted as answers and similar. Also keep in mind that posts receiving not-an-answer flags are sent to this queue.
Therefore clicking looks OK basically means that:
- An answer really is an honest attempt to answer the question.
- A question is a valid question for this site (and should not be closed).
- I cannot improve that post anymore.
- The post is understandable.
Only the last two points are somewhat correlated with the overall quality of that post but only that: correlated. Therefore it can very well be that I decide that a post looks OK which has a much lower overall quality than the next post for which I recommend deletion, e.g., because it is just a misplaced answer. Or, more abstractly: The quality distributions of posts that pass the low-quality queue and those that fail it strongly overlap.
However, as long as that button is named anything like Looks OK, Not Awful or Meh, this implies that clicking this button asserts that a post has passed some quality threshold. And this leads to incorrect reviews, frustrated users, in particular new ones (see my last section in this answer) and dispute.
Finally, I would like to remark that the current naming of that button would only be half as bad if the corresponding help text would be more accurate – see Improve low-quality-post-queue help text.