One thing that I've become more sure of as time goes on is that most people are incompetent critics of literary works. There are lots of different kinds of incompetent critics. There's the incompetent critic who has his personal tastes and absolutely refuses to recognize anything not conforming to them. There's the incompetent critic who is always complaining about the fact that the story is not the one he would have written -- this one usually makes me want to strangle him. There's the incompetent critic who has some abstract theory or standard in his head, which is then applied mechanically and without regard for circumstances. There's the critic who makes definitive judgments about works that he hasn't read. There are many others.
There's nothing wrong with being an incompetent critic, per se, but it's quite important to recognize that there is incompetence in criticism. It is at least sometimes provable that criticism is incompetent -- the most obvious cases come from the person who clearly is getting facts about the work wrong, but you can often find critics engaging in bizarre kinds of reasoning, or just stubborn repetition without any appropriate and relevant reasons. And it's worth noting that being a 'reader' doesn't make you a competent critic.
The philosophers of the Scottish Enlightenment did a lot of work on critical competence -- good taste, as they called it -- and they noted that good taste requires extensive experience, the ability to draw relevant distinctions, and a sympathetic understanding of human beings generally. All of these are things that can be rationally assessed.
Increasingly, however, I have come to think that one of the common characteristics, and perhaps the distinguishing feature, of incompetent criticism is not recognizing that skill is skill, that craft has the structure of craft. All skill or craft has goals in view; the whole point of skill is that it appropriately applies means to achieve goals and does so successfully. Over and over again I see in book reviews, incomments on blogs, in recommendations for people trying to do NaNoWriMo, and in a thousand other venues, a common failure to evaluate a literary work in terms of the only ways it can actually be evaluated as a work at all: the ends sought, the means used to accomplish those ends, and the many and various excellences in the way the author uses the means to accomplish the ends. If we strip away all irrelevancies, all purely arbitrary and irrational criteria, there is nothing about a work itself that can be assessed except these three things:
(1) Are the ends sought genuinely good?
(2) Are the means appropriate to the end?
(3) Are the means used in a way to achieve the end well?
I thus lay it down as a rule: If you cannot identify what the author is trying to do, your opinion about the work is of no importance at all. It does not matter whether you were bored. It does not matter whether you have ideas about how you think it should have been written. It does not matter whether you hated it. It does not matter whether you liked it. If you don't know what the author is doing, or if you've misunderstood what the author is doing, your judgment is about you, and says nothing about the work itself.
Now, of course, there are layers and layers to this. Unless a writer is crafting tiny, standalone poetic gems, he or she will always be doing more than one thing (and perhaps not even then). One of the things that is true of practically all of the great masters is that they are doing lots of things simultaneously. You can read Jane Austen as light fiction, because she is doing light-fiction things like funny characters and romantic plots. You can read Jane Austen as profound social criticism because all her works do engage in social criticism. You can read Jane Austen as moral philosophy because all her works explore questions in moral philosophy. They are all built into the novels, and you can explore any or all of them. But the competence of your judgement about the novels depends entirely on your ability to see some of them, and the significance of your evaluation does not go beyond the ends you've understood.
All of the bad critics mentioned at the beginning of this post obviously fail to treat the craft as a craft, as the effective application of means to achieve productive ends. If you look at famously bad critical reviews, like Edmund Wilson's attack on Tolkien's Lord of the Rings, you can see at every turn that they make this error. It even shows some of the problems of subtler failings in criticism, like attacking competent writers for not being authorial geniuses, which shows that you have no respect for the craft. If you attack Alfred Austin simply for not being as great as Tennyson, this does not show your good taste but your stupidity; it shows that you are a poser with no sense of good poetic workmanship, and are not able to give an account of when a poet is using good means in an appropriate way to accomplish poetic ends. That is what it is to assess the craftsmanship of a piece.
Of course, everything said here about literary criticism applies equally to any other critical evaluation of some product of artisanship, whether it be paintings or buildings or food or philosophical arguments.